文字

date

(PHP 4, PHP 5, PHP 7)

date — 格式化一个本地时间／日期

说明

string date ( string $format [, int $timestamp ] )

返回将整数 timestamp 按照给定的格式字串而产生的字符串。如果没有给出时间戳则使用本地当前时间。换句话说，timestamp 是可选的，默认值为 time() 。

Tip

自 PHP 5.1.1 起有几个有用的常量可用作标准的日期／时间格式来指定 format 参数。

Tip

自 PHP 5.1 起在 $_SERVER['REQUEST_TIME'] 中保存了发起该请求时刻的时间戳。

Note:

有效的时间戳典型范围是格林威治时间 1901 年 12 月 13 日 20:45:54 到 2038 年 1 月 19 日 03:14:07。（此范围符合 32 位有符号整数的最小值和最大值）。不过在 PHP 5.1 之前此范围在某些系统（如 Windows）中限制为从 1970 年 1 月 1 日到 2038 年 1 月 19 日。

Note:

要将字符串表达的时间转换成时间戳，应该使用 strtotime() 。此外一些数据库有一些函数将其时间格式转换成时间戳（例如 MySQL 的 » UNIX_TIMESTAMP 函数）。

**格式字串可以识别以下 `format` 参数的字符串**
`format` 字符	说明	返回值例子
日	---	---
d	月份中的第几天，有前导零的 2 位数字	01 到 31
D	星期中的第几天，文本表示，3 个字母	Mon 到 Sun
j	月份中的第几天，没有前导零	1 到 31
l（“L”的小写字母）	星期几，完整的文本格式	Sunday 到 Saturday
N	ISO-8601 格式数字表示的星期中的第几天（PHP 5.1.0 新加）	1（表示星期一）到 7（表示星期天）
S	每月天数后面的英文后缀，2 个字符	st，nd，rd 或者 th。可以和 j 一起用
w	星期中的第几天，数字表示	0（表示星期天）到 6（表示星期六）
z	年份中的第几天	0 到 365
星期	---	---
W	ISO-8601 格式年份中的第几周，每周从星期一开始（PHP 4.1.0 新加的）	例如：42（当年的第 42 周）
月	---	---
F	月份，完整的文本格式，例如 January 或者 March	January 到 December
m	数字表示的月份，有前导零	01 到 12
M	三个字母缩写表示的月份	Jan 到 Dec
n	数字表示的月份，没有前导零	1 到 12
t	给定月份所应有的天数	28 到 31
年	---	---
L	是否为闰年	如果是闰年为 1，否则为 0
o	ISO-8601 格式年份数字。这和 Y 的值相同，只除了如果 ISO 的星期数（W）属于前一年或下一年，则用那一年。（PHP 5.1.0 新加）	Examples: 1999 or 2003
Y	4 位数字完整表示的年份	例如：1999 或 2003
y	2 位数字表示的年份	例如：99 或 03
时间	---	---
a	小写的上午和下午值	am 或 pm
A	大写的上午和下午值	AM 或 PM
B	Swatch Internet 标准时	000 到 999
g	小时，12 小时格式，没有前导零	1 到 12
G	小时，24 小时格式，没有前导零	0 到 23
h	小时，12 小时格式，有前导零	01 到 12
H	小时，24 小时格式，有前导零	00 到 23
i	有前导零的分钟数	00 到 59>
s	秒数，有前导零	00 到 59>
u	毫秒（PHP 5.2.2 新加）。需要注意的是 date() 函数总是返回 000000 因为它只接受 integer 参数，而 DateTime::format() 才支持毫秒。	示例: 654321
时区	---	---
e	时区标识（PHP 5.1.0 新加）	例如：UTC，GMT，Atlantic/Azores
I	是否为夏令时	如果是夏令时为 1，否则为 0
O	与格林威治时间相差的小时数	例如：+0200
P	与格林威治时间（GMT）的差别，小时和分钟之间有冒号分隔（PHP 5.1.3 新加）	例如：+02:00
T	本机所在的时区	例如：EST，MDT（【译者注】在 Windows 下为完整文本格式，例如“Eastern Standard Time”，中文版会显示“中国标准时间”）。
Z	时差偏移量的秒数。UTC 西边的时区偏移量总是负的，UTC 东边的时区偏移量总是正的。	-43200 到 43200
完整的日期／时间	---	---
c	ISO 8601 格式的日期（PHP 5 新加）	2004-02-12T15:19:21+00:00
r	RFC 822 格式的日期	例如：Thu, 21 Dec 2000 16:01:07 +0200
U	从 Unix 纪元（January 1 1970 00:00:00 GMT）开始至今的秒数	参见 time()

格式字串中不能被识别的字符将原样显示。Z 格式在使用 gmdate() 时总是返回 0。

Example #1 date() 例子

  <?php
 // 设定要用的默认时区。自 PHP 5.1 可用
 date_default_timezone_set ( 'UTC' );


 // 输出类似：Monday
 echo  date ( "l" );

 // 输出类似：Monday 15th of August 2005 03:12:46 PM
 echo  date ( 'l dS \of F Y h:i:s A' );

 // 输出：July 1, 2000 is on a Saturday
 echo  "July 1, 2000 is on a "  .  date ( "l" ,  mktime ( 0 ,  0 ,  0 ,  7 ,  1 ,  2000 ));

 
// 输出类似：Wed, 25 Sep 2013 15:28:57 -0700
 echo  date ( DATE_RFC2822 );

 // 输出类似：2000-07-01T00:00:00+00:00
 echo  date ( DATE_ATOM ,  mktime ( 0 ,  0 ,  0 ,  7 ,  1 ,  2000 ));
 ?>

在格式字串中的字符前加上反斜线来转义可以避免它被按照上表解释。如果加上反斜线后的字符本身就是一个特殊序列，那还要转义反斜线。

Example #2 在 date() 中转义字符

  <?php
 // prints something like: Wednesday the 15th
 echo  date ( "l \\t\h\e jS" );
 ?>

可以把 date() 和 mktime() 函数结合使用来得到未来或过去的日期。

Example #3 date() 和 mktime() 例子

  <?php
$tomorrow   =  mktime ( 0 ,  0 ,  0 ,  date ( "m" )  ,  date ( "d" )+ 1 ,  date ( "Y" ));
 $lastmonth  =  mktime ( 0 ,  0 ,  0 ,  date ( "m" )- 1 ,  date ( "d" ),    date ( "Y" ));
 $nextyear   =  mktime ( 0 ,  0 ,  0 ,  date ( "m" ),    date ( "d" ),    date ( "Y" )+ 1 );
 ?>

Note:

由于夏令时的缘故，这种方法比简单地在时间戳上加减一天或者一个月的秒数更可靠。

一些使用 date() 格式化日期的例子。注意要转义所有其它的字符，因为目前有特殊含义的字符会产生不需要的结果，而其余字符在 PHP 将来的版本中可能会被用上。当转义时，注意用单引号以避免类似 \n 的字符变成了换行符。

Example #4 date() 格式举例

  <?php
 // 假定今天是：March 10th, 2001, 5:16:18 pm
 $today  =  date ( "F j, Y, g:i a" );                  // March 10, 2001, 5:16 pm
 $today  =  date ( "m.d.y" );                          // 03.10.01
 $today  =  date ( "j, n, Y" );                        // 10, 3, 2001
 $today  =  date ( "Ymd" );                            // 20010310
 $today  =  date ( 'h-i-s, j-m-y, it is w Day z ' );   // 05-16-17, 10-03-01, 1631 1618 6 Fripm01
 $today  =  date ( '\i\t \i\s \t\h\e jS \d\a\y.' );    // It is the 10th day.
 $today  =  date ( "D M j G:i:s T Y" );                // Sat Mar 10 15:16:08 MST 2001
 $today  =  date ( 'H:m:s \m \i\s\ \m\o\n\t\h' );      // 17:03:17 m is month
 $today  =  date ( "H:i:s" );                          // 17:16:17
 $today  =  date ( "Y-m-d H:i:s" );                    // 2001-03-10 17:16:18 （MySQL DATETIME 格式）
 ?>

要格式化其它语种的日期，应该用 setlocale() 和 strftime() 函数来代替 date() 。

参见 getlastmod() ， gmdate() ， mktime() ， strftime() 和 time() 。

参数

format

输出的日期 string 格式。参见下文中的格式化选项。同时，还可以使用预定义日期常量，例如：常量 DATE_RSS 表示格式化字符串 'D, d M Y H:i:s'。

**`format` 参数字符串中可识别下列字符**
`format` 字符	描述	返回值示例
天	---	---
d	一个月中的第几天，有前导 0 的 2 位数字	从 01 到 31
D	3 个字符表示的星期几	从 Mon 到 Sun
j	一个月中的第几天，无前导 0	从 1 到 31
l (lowercase 'L')	星期几，英文全称	从 Sunday 到 Saturday
N	ISO-8601 规定的数字表示的星期几（PHP 5.1.0 新加）	从 1 （表示星期一）到 7 （表示星期日）
S	一个月中的第几天，带有 2 个字符表示的英语序数词。	st， nd， rd 或者 th。可以和 j 联合使用。
w	数字表示的星期几	从 0 （星期日）到 6 （星期六）
z	一年中的第几天，从 0 开始计数	从 0 到 365
周	---	---
W	ISO-8601 规范的一年中的第几周，周一视为一周开始。（PHP 4.1.0 新加）	示例： 42 （本年第42周）
月	---	---
F	月份英文全拼，例如：January 或 March	从 January 到 December
m	带有 0 前导的数字表示的月份	从 01 到 12
M	3 个字符表示的月份的英文简拼	从 Jan 到 Dec
n	月份的数字表示，无前导 0	1 through 12
t	给定月份中包含多少天	从 28 到 31
年	---	---
L	是否为闰年	如果是闰年，则返回 1，反之返回 0。
o	ISO-8601 规范的年份，同 Y 格式。有一种情况除外：当 ISO 的周数（W）属于前一年或者后一年时，会返回前一年或者后一年的年份数字表达。属于前一年或者后一年时，会返回前一年或者后一年的年份数字表达。（PHP 5.1.0 新加）	示例：1999 或 2003
Y	4 位数字的年份	示例：1999 或 2003
y	2 位数字的年份	示例： 99 或 03
时间	---	---
a	上午还是下午，2 位小写字符	am 或 pm
A	上午还是下午，2 位大写字符	AM 或 PM
B	斯沃琪因特网时间	从 000 到 999
g	小时，12时制，无前导 0	从 1 到 12
G	小时，24时制，无前导 0	从 0 到 23
h	小时，12时制，有前导 0 的 2 位数字	从 01 到 12
H	小时，24时制，有前导 0 的 2 位数字	00 through 23
i	分钟，有前导 0 的 2 位数字	从 00 到 59
s	秒，有前导 0 的 2 位数字	从 00 到 59
u	毫秒（PHP 5.2.2 新加）	示例： 654321
时区	---	---
e	时区标识（PHP 5.1.0 新加）	示例: UTC, GMT, Atlantic/Azores
I （大写字母 i）	是否夏令时	如果是夏令时则返回 1，反之返回 0。
O	和格林威治时间（GMT）的时差，以小时为单位	示例： +0200
P	和格林威治时间（GMT）的时差，包括小时和分钟，小时和分钟之间使用冒号（:）分隔（PHP 5.1.3 新加）	示例： +02:00
T	时区缩写	示例：EST, MDT ...
Z	以秒为单位的时区偏移量。UTC 以西的时区返回负数，UTC 以东的时区返回正数。	从 -43200 到 50400
完整的日期/时间	---	---
c	ISO 8601 日期及时间（PHP 5 新加）	2004-02-12T15:19:21+00:00
r	» RFC 2822 格式的日期和时间	示例：Thu, 21 Dec 2000 16:01:07 +0200
U	自 1970 年 1 月 1 日 0 时 0 分 0 秒（GMT 时间）以来的时间，以秒为单位	参见 time()

格式化字符串中的不可识别字符将原样输出。当使用 gmdate() 函数时， Z 格式永远返回 0。

Note:

由于本函数仅接受 integer 类型的时间戳参数，所以 u 格式仅在使用 date_format() 函数并且使用 date_create() 函数创建时间戳时才是有用的。

timestamp

可选的 timestamp 参数是一个 integer 的 Unix 时间戳，如未指定，参数值默认为当前本地时间。也就是说，其值默认为 time() 的返回值。

返回值

返回格式化后的日期时间的字符串表达。如果 timestamp 参数不是一个有效数值，则返回 FALSE 并引发 E_WARNING 级别的错误。

错误／异常

在每次调用日期/时间函数时，如果时区无效则会引发 E_NOTICE 错误，如果使用系统设定值或 TZ 环境变量，则会引发 E_STRICT 或 E_WARNING 消息。参见 date_default_timezone_set() 。

更新日志

版本	说明
5.1.0	时间戳的有效取值范围为 GMT 时间的 1901 年 12 月 13 日至 GMT 时间的 2038 年 1 月 19 日。（32 位有符号整数的取值范围）。但是，在 PHP 5.1.0 之前的版本，在某些系统（例如 Windows）上有效取值范围为 1970 年 1 月 1 日至 2038 年 1 月 19 日。
5.1.0	现在发布 `E_STRICT` 和 `E_NOTICE` 时区错误。
5.1.1	`format` 参数标准的可用日期/时间格式常量见：常量

范例

Example #5 date() 函数示例

  <?php
 // 设置默认时区。PHP 5.1 之后版本可用
 date_default_timezone_set ( 'UTC' );


 // 输出类似： Monday
 echo  date ( "l" );

 // 输出类似：Monday 8th of August 2005 03:12:46 PM
 echo  date ( 'l jS \of F Y h:i:s A' );

 // 输出：July 1, 2000 is on a Saturday
 echo  "July 1, 2000 is on a "  .  date ( "l" ,  mktime ( 0 ,  0 ,  0 ,  7 ,  1 ,  2000 ));

 
// 输出类似： Mon, 15 Aug 2005 15:12:46 UTC
 echo  date ( DATE_RFC822 );

 // 输出类似：2000-07-01T00:00:00+00:00
 echo  date ( DATE_ATOM ,  mktime ( 0 ,  0 ,  0 ,  7 ,  1 ,  2000 ));
 ?>

可以使用反斜线进行转义来阻止函数解析格式字符串中的可识别字符。如果反斜线和要转义的字符连在一起依然是一个有效的字符序列，那么需要对反斜线再次进行转义。

Example #6 对 date() 函数中的格式字符串进行转义

  <?php
 // 输出类似： Wednesday the 15th
 echo  date ( 'l \t\h\e jS' );
 ?>

可以联合使用 date() 和 mktime() 函数来构造之前或者之后的日期时间。

Example #7 date() 和 mktime() 联合使用示例

  <?php
$tomorrow   =  mktime ( 0 ,  0 ,  0 ,  date ( "m" )  ,  date ( "d" )+ 1 ,  date ( "Y" ));
 $lastmonth  =  mktime ( 0 ,  0 ,  0 ,  date ( "m" )- 1 ,  date ( "d" ),    date ( "Y" ));
 $nextyear   =  mktime ( 0 ,  0 ,  0 ,  date ( "m" ),    date ( "d" ),    date ( "Y" )+ 1 );
 ?>

Note:

由于存在夏令时时间，所以此方案相对于直接在时间戳上加/减秒数要更加可靠。

date() 函数格式化的一些示例。需要注意的是，即使是对于当前来说并不具有特殊含义的字符，也要像对待具有特殊含义的字符那样进行转义，以避免函数返回非预期的值。因为可能在将来的 PHP 版本中，这些字符会被赋予特殊的含义。进行转义的时候，请确保使用单引号，以避免 \n 被解释为换行符号。

Example #8 date() 函数格式化

  <?php
 // 假设今天是 2001 年 3 月 10 日下午 5 点 16 分 18 秒，
// 并且位于山区标准时间（MST）时区

 $today  =  date ( "F j, Y, g:i a" );                  // March 10, 2001, 5:16 pm
 $today  =  date ( "m.d.y" );                          // 03.10.01
 $today  =  date ( "j, n, Y" );                        // 10, 3, 2001
 $today  =  date ( "Ymd" );                            // 20010310
 $today  =  date ( 'h-i-s, j-m-y, it is w Day' );      // 05-16-18, 10-03-01, 1631 1618 6 Satpm01
 $today  =  date ( '\i\t \i\s \t\h\e jS \d\a\y.' );    // it is the 10th day.
 $today  =  date ( "D M j G:i:s T Y" );                // Sat Mar 10 17:16:18 MST 2001
 $today  =  date ( 'H:m:s \m \i\s\ \m\o\n\t\h' );      // 17:03:18 m is month
 $today  =  date ( "H:i:s" );                          // 17:16:18
 ?>

如果需要将日期时间格式化为其他语言，你应该使用 setlocale() 和 strftime() 函数来替代 date() 函数。

注释

Note:

使用 strtotime() 函数将一个字符串表达的日期时间转换为时间戳。另外，一些数据库产品也提供了将日期时间格式转换为时间戳的函数。（例如 MySQL 中的 » UNIX_TIMESTAMP 函数）。

Tip

从 PHP 5.1 版本开始，请求的开始时间可以从变量 $_SERVER['REQUEST_TIME'] 中获取。

参见

gmdate() - 格式化一个 GMT/UTC 日期／时间
idate() - 将本地时间日期格式化为整数
getdate() - 取得日期／时间信息
getlastmod() - 获取页面最后修改的时间
mktime() - 取得一个日期的 Unix 时间戳
strftime() - 根据区域设置格式化本地时间／日期
time() - 返回当前的 Unix 时间戳
strtotime() - 将任何英文文本的日期时间描述解析为 Unix 时间戳
预定义的日期时间常量

用户评论:

[#1] tkachenko_ivan at bk dot ru [2015-11-01 13:47:49]

<?php function strftimeFormatToDate($strftimeFormat) { $caracs = array( "%d" => "d", "%a" => "D", "%e" => "j", "%A" => "l", "%u" => "N", "%w" => "w", "%j" => "z", "%V" => "W", "%B" => "F", "%m" => "m", "%b" => "M", "%G" => "o", "%Y" => "Y", "%y" => "y", "%P" => "a", "%p" => "A", "%l" => "g", "%I" => "h", "%H" => "H", "%M" => "i", "%S" => "s", "%z" => "O", "%Z" => "T", "%s" => "U", ); return strtr((string)$strftimeFormat, $caracs); } $strftimeFormat = '%Y-%m-%d %H:%M:%S'; $formatDate = strftimeFormatToDate($strftimeFormat); // Y-m-d H:i:s ?>

[#2] krejci dot info at seznam dot cz [2015-09-01 12:22:24]

I recommend to use "/" instead of "-" when creating dates:

<?php if( date( 'd/m' ) >= date_create( '01/09' ) ) { } ?>

[#3] akshayinbox at gmail dot com [2015-08-23 18:46:54]

When using date(), be sure to "double-escape" certain characters, for example, if printing the word "at", double escape "t" otherwise it will be treated as "tab" simply leading to a space being inserted.

Example:
<?php echo "Last updated ".date("M j<\s\u\p>S</\s\u\p\>, Y \a\\t h:i A"); ?>

will output
Last updated Aug 23rd 2015 at 2:47 PM

(assuming today is Aug 23rd 2015 and it is 2:47 PM)

[#4] sanket at webvice dot co dot uk [2015-08-19 13:23:06]

<?php function getWorkingDays($date,$buffer=1,$holidays='') { if ($holidays==='') $holidays = 'https://www.gov.uk/bank-holidays/england-and-wales.ics'; if (!is_array($holidays)) { $ch = curl_init($holidays); curl_setopt($ch,CURLOPT_RETURNTRANSFER,true); $ics = curl_exec($ch); curl_close($ch); $ics = explode("\n",$ics); $ics = preg_grep('/^DTSTART;/',$ics); $holidays = preg_replace('/^DTSTART;VALUE=DATE:(\\d{4})(\\d{2})(\\d{2}).*/s','$1-$2-$3',$ics); } $addDay = 0; while ($buffer--) { while (true) { $addDay++; $newDate = date('Y-m-d', strtotime("$date +$addDay Days")); $newDayOfWeek = date('w', strtotime($newDate)); if ( $newDayOfWeek>0 && $newDayOfWeek<6 && !in_array($newDate,$holidays)) break; } } return $newDate; } ?>

[#5] ivijan dot stefan at gmail dot com [2015-03-20 16:45:36]

If you have a problem with the different time zone, this is the solution for that.
<?php // first line of PHP $defaultTimeZone='UTC'; if(date_default_timezone_get()!=$defaultTimeZone)) date_default_timezone_set($defaultTimeZone); // somewhere in the code function _date($format="r", $timestamp=false, $timezone=false) { $userTimezone = new DateTimeZone(!empty($timezone) ? $timezone : 'GMT'); $gmtTimezone = new DateTimeZone('GMT'); $myDateTime = new DateTime(($timestamp!=false?date("r",(int)$timestamp):date("r")), $gmtTimezone); $offset = $userTimezone->getOffset($myDateTime); return date($format, ($timestamp!=false?(int)$timestamp:$myDateTime->format('U')) + $offset); } echo 'System Date/Time: '.date("Y-m-d | h:i:sa").'<br>'; echo 'New York Date/Time: '._date("Y-m-d | h:i:sa", false, 'America/New_York').'<br>'; echo 'Belgrade Date/Time: '._date("Y-m-d | h:i:sa", false, 'Europe/Belgrade').'<br>'; echo 'Belgrade Date/Time: '._date("Y-m-d | h:i:sa", 514640700, 'Europe/Belgrade').'<br>'; ?>
This is the best and fastest solution for this problem. Working almost identical to date() function only as a supplement has the time zone option.

[#6] Ryan [2014-10-20 14:15:55]

That is just too hard anyone have it easier terms for a lad who only has internet for 5 mis a day cause he has to walk his pet peanut

[#7] jock [2014-06-17 14:27:26]

As of PHP 5.3.3, date('c') will produce a string like this:

2014-06-17T16:22:42+02:00

Instead date (DATE_ISO8601) will produce:

2014-06-17T16:23:36+0200

which lacks the semicolon in the timezone part. Both are ISO8601 compliant anyway, but I found that the latter has better compatibility with other languages like python.

[#8] david dot leon at gmx dot com [2014-05-19 10:44:37]

<?php //date returns microseconds. function mdate($format, $microtime = null) { $microtime = explode(' ', ($microtime ? $microtime : microtime())); if (count($microtime) != 2) return false; $microtime[0] = $microtime[0] * 1000000; $format = str_replace('u', $microtime[0], $format); return date($format, $microtime[1]); } ?>

echo mdate('Y-m-d H:i:s.u');

2014-05-19 12:41:59.202303

[#9] Manu Manjunath [2014-04-11 11:59:09]

If you want to use "u" format specifier for micrseconds without changing to DateTime object, you may write a function as below:
<?php function date_with_micro($format, $timestamp = null) { if (is_null($timestamp) || $timestamp === false) { $timestamp = microtime(true); } $timestamp_int = (int) floor($timestamp); $microseconds = (int) round(($timestamp - floor($timestamp)) * 1000000.0, 0); $format_with_micro = str_replace("u", $microseconds, $format); return date($format_with_micro, $timestamp_int); } ?>

You can safely replace your date() function with date_with_micro().

[#10] Anonymous [2014-03-10 09:09:40]

It's common for us to overthink the complexity of date/time calculations and underthink the power and flexibility of PHP's built-in functions. Consider http://php.net/manual/en/function.date.php#108613

<?php
function get_time_string($seconds)
{
return date('H:i:s', strtotime("2000-01-01 + $seconds SECONDS"));
}

[#11] matthew dot hotchen at worldfirst dot com [2014-01-30 10:25:33]

FYI: there's a list of constants with predefined formats on the DateTime object, for example instead of outputting ISO 8601 dates with:

<?php echo date('c'); ?>

or

<?php echo date('Y-m-d\TH:i:sO'); ?>

You can use

<?php echo date(DateTime::ISO8601); ?>

instead, which is much easier to read.

[#12] ttt_joe_08 [2014-01-20 02:43:23]

Just FYI, it's more appropriate to say "UTC", not "GMT". GMT was given up in 1972 and UTC is now the proper way. The reason being G stands for Greenwich, which naturally upset some people.

[#13] Jacques Marais [2014-01-14 07:45:08]

If you want to print something like: ?Tuesday, the 14th of January, 2014

Use this:

<?php echo date("l", strtotime("now")).', the'.date(" jS", strtotime("now")).' of'.date(" F, Y", strtotime("now")); ?>

This is because you cannot use words in the date string. If you use words in the date string it will be seen as a format character

So if you use:

<?php echo date("l, the jS of F, Y", strtotime("now")); ?>

It will print something like: Tuesday, 3108Europe/Berlin 14th 2014f January, 2014

[#14] Anonymous [2013-12-11 20:21:50]

To quickly convert date("N") to a 0 based index with Sunday being represented as 0, you can run it against modulus 7:

<?php $first_of_month_index = date('N', strtotime('4/1/1990')) % 7; ?>

[#15] adityabhai at gmail dot com [2013-10-08 13:57:04]

For Microseconds, we can get by following:

echo date('Ymd His'.substr((string)microtime(), 1, 8).' e');

Thought, it might be useful to someone !

[#16] Anonymous [2013-05-31 07:35:14]

Was trying to compare dates when I noticed that:

<?php var_dump(date('d.m.Y', null));//string(10) "01.01.1970" var_dump(date('d.m.Y', ''));//bool(false) ?>

Thought it's worth mentioning. Caused some weird logs to be produced in our system since this does not evaluate to the same.

[#17] scott at keenot dot es [2013-05-23 12:28:56]

If anyone needs a really fast function for converting a datetime string (i.e. as retrieved from a MySQL DATETIME entry) into a human-friendly time output analogous to date($format, $time), here's a useful function.

<?php function fdate($datetimestring = '1970-01-01 00:00:00', $format = 'U') { // Create a datetime object, return it formatted // If you want to give credit for this somewhere, thanks. // You really don't have to though; this is kinda obvious $dt = new DateTime($datetimestring); return $dt->format($format); } ?>

The main purpose of this is to reduce lines of code and allow inline coding. For example:
<?php echo "This page was submitted on ".fdate($row['created'], 'F j, Y g:i:s A')." and last modified ".fdate($row['modified'], 'F j, Y g:i:s A')."<br />\n"; ?>

[#18] FiraSEO [2013-02-28 07:23:44]

this how you make an HTML5 <time> tag correctly

<?php echo '<time datetime="'.date('c').'">'.date('Y - m - d').'</time>'; ?>

in the "datetime" attribute you should put a machine-readable value which represent time , the best value is a full time/date with ISO 8601 ( date('c') ) ,,, the attr will be hidden from users

and it doesn't really matter what you put as a shown value to the user,, any date/time format is okay !

This is very good for SEO especially search engines like Google .

[#19] Anonymous [2012-10-12 09:43:40]

To find last sunday for given date

<?php $day = '2012-10-04'; echo 'last sunday : '.date("Y-m-d",strtotime($day." last Sunday ")); ?>

output:

last sunday : 2012-09-30

[#20] Chris [2012-08-19 04:46:24]

Use this to convert the local/UTC hour to the UTC/local hour:

<?php for($utc_to_local = array(), $offset = date('Z'), $h = 0; $h < 24; $utc_to_local[] = date('G', mktime($h++)+$offset)); $local_to_utc = array_flip($utc_to_local); echo "2 am local is ", $local_to_utc[2], " UTC"; echo "3 pm UTC is ", $utc_to_local[15], " local"; ?>

This is useful when you need to do many conversions. Lookup tables are faster than calling date() and mktime() multiple times.

[#21] stokestack at gmail dot com [2012-07-31 21:37:52]

If you want to find your server's timezone offset from GMT, it seems as though you could just do:

date('Z')

to get the number of seconds offset. But PHP requires that you call date_default_timezone_set(). So if you have to hard-code a timezone, why not simply hard-code a variable that tells you the offset from GMT? If you set the timezone to GMT, the dates in your database will still be in local time, but time('Z') will return zero.

To keep your code portable across servers in different timezones, you can do this:

date_default_timezone_set(date_default_timezone_get())

This keeps PHP from complaining that you haven't called date_default_timezone_set(), but makes your code portable. Ridiculous.

[#22] webmaster1989 at gmail dot com [2012-07-27 22:59:31]

Sometimes it is very useful to convert a sql timestamp to an also called NTP time. This is often used as time date notation in XML RSS pages. To convert a timestamp to this NTP notation try the following:

<?php echo date('D, d M Y h:i:s O', strtotime ($timestamp); ?>

[#23] Leopietroni [2012-07-26 09:23:29]

This function will add working day to a given timestamp

<?php function addworkinday($timestamp,$daystoadd){ $dayoftheweek = date("N",$timestamp); $sum =$dayoftheweek +$daystoadd; while ($sum >= 6) { $daystoadd=$daystoadd+1; $sum=$sum-1; } return $timestamp +(60*60*24*$daystoadd); } ?>

[#24] lehal2 at hotmail dot com [2012-07-04 14:44:53]

here is an example how you can make numeric days of the week from 1 to 7(Monday to Friday)

<?php $currentdate = mktime(0, 0, 0, date("m") , date("d"), date("Y")); echo $day_eg1 = date ('N',$currentdate); echo $day_eg2 = date("N", $today+1 * 24 * 3600); echo $day_eg3= date("N", $today+2 * 24 * 3600); echo $day_eg4 = date("N", $today+3 * 24 * 3600); echo $day_eg5 = date("N", $today+4 * 24 * 3600); echo $day_eg6 = date("N", $today+5 * 24 * 3600); echo $day_eg7 = date("N", $today+6 * 24 * 3600); ?>

[#25] m_ocx at yahoo dot com [2012-06-14 16:36:40]

Here is a cool Date class to implement the date function:

<?php class Date { private $shortDateFormat = "F j, Y"; private $longDateFormat = "F j, Y, g:i a"; private $timestamp = 0; function __construct($timestamp = 0) { $this->timestamp = $timestamp; } public function getTime() { return (int) $this->timestamp; } public function long() { if ( $this->timestamp > 0 ) { return date ( $this->longDateFormat , $this->timestamp ); } else { return ""; } } public function short() { if ( $this->timestamp > 0 ) { return date ( $this->shortDateFormat , $this->timestamp ); } else { return ""; } } public function __toString() { return $this->timestamp; } } ?>

[#26] Tim Connolly [2012-06-13 14:56:45]

Here's my solution for looking up the month number by name (used when parsing an 'ls'):

<?php for($m=1;$m<=12;$m++){ $month=date("M",mktime(0,0,0,$m,1,2000)); $mon["$month"]=$m; } ?>

[#27] Anon [2012-05-10 20:24:48]

I needed to convet a duration timestamp into H:i:s but whenever I did it kept bringing 5 back as 01:00:05 (due to some DST stuff) so I made this function to replace date(). It has no optimisations but hopefully someone might find it useful:

<?php function get_time_string(){ $time = 3600+(60*32)+(50); // 01:32:50 $time_string = ''; $hours = (int)($time/(60*60)); if(strlen($hours) > 1){ $time_string = $hours.':'; }else{ $time_string = '0'.$hours.':'; } $minutes = (int)(($time%(60*60))/(60)); if($minutes >= 1){ if(strlen($minutes) > 1){ $time_string .= $minutes.':'; }else{ $time_string .= '0'.$minutes.':'; } $seconds = ($time%(60*60))%(60); if(strlen($seconds) > 1){ $time_string .= $seconds; }else{ $time_string .= '0'.$seconds; } }else{ if(strlen($time) > 1){ $time_string .= '00:'.$time; }else{ $time_string .= '00:0'.$time; } } return $time_string; } ?>

[#28] nathan [2012-05-03 00:32:42]

<?php $day=date("l"); $date=date("j"); $suffix=date("S"); $month=date("F"); $year=date("Y"); echo $day . ", " . $month . " " . $date . $suffix . ", " . $year; ?>

rudimentary, simple way to due things, but it gets the job done for someone learning more on the subject.

[#29] matt [2012-03-23 22:23:43]

date() has some strange behavior at extremely high values:

<?php echo "9223372036854775805: " . date("Y-m-d g:i:s a", 9223372036854775805) . "\n"; echo "9223372036854775806: " . date("Y-m-d g:i:s a", 9223372036854775806) . "\n"; echo "9223372036854775807: " . date("Y-m-d g:i:s a", 9223372036854775807) . " (0x7FFFFFFFFFFFFFFF)\n"; echo "9223372036854775808: " . date("Y-m-d g:i:s a", 9223372036854775808) . "\n"; echo "9223372036854775809: " . date("Y-m-d g:i:s a", 9223372036854775809) . "\n"; echo "9223372036854775810: " . date("Y-m-d g:i:s a", 9223372036854775810) . "\n"; echo "...\n"; echo "9223372036854776832: " . date("Y-m-d g:i:s a", 9223372036854776832) . "\n"; echo "9223372036854776833: " . date("Y-m-d g:i:s a", 9223372036854776833) . "\n"; echo "...\n"; echo "9223372036854778879: " . date("Y-m-d g:i:s a", 9223372036854778879) . "\n"; echo "9223372036854778880: " . date("Y-m-d g:i:s a", 9223372036854778880) . "\n"; echo "...\n"; echo "9223372036854780928: " . date("Y-m-d g:i:s a", 9223372036854780928) . "\n"; echo "9223372036854780929: " . date("Y-m-d g:i:s a", 9223372036854780929) . "\n"; echo "...\n"; echo "9223372036854782975: " . date("Y-m-d g:i:s a", 9223372036854782975) . "\n"; echo "9223372036854782976: " . date("Y-m-d g:i:s a", 9223372036854782976) . "\n"; echo "...\n"; echo "9223372036854785024: " . date("Y-m-d g:i:s a", 9223372036854785024) . "\n"; echo "9223372036854785025: " . date("Y-m-d g:i:s a", 9223372036854785025) . "\n"; echo "...\n"; echo "9223372036854787071: " . date("Y-m-d g:i:s a", 9223372036854787071) . "\n"; echo "9223372036854787072: " . date("Y-m-d g:i:s a", 9223372036854787072) . "\n"; echo "...\n"; echo "9223372036854789120: " . date("Y-m-d g:i:s a", 9223372036854789120) . "\n"; echo "9223372036854789121: " . date("Y-m-d g:i:s a", 9223372036854789121) . "\n"; echo "...\n"; echo "9223372036854791167: " . date("Y-m-d g:i:s a", 9223372036854791167) . "\n"; echo "9223372036854791168: " . date("Y-m-d g:i:s a", 9223372036854791168) . "\n"; echo "...\n"; echo "9223372036854793215: " . date("Y-m-d g:i:s a", 9223372036854793215) . "\n"; echo "9223372036854793216: " . date("Y-m-d g:i:s a", 9223372036854793216) . "\n"; echo "9223372036854793217: " . date("Y-m-d g:i:s a", 9223372036854793217) . "\n"; echo "9223372036854793218: " . date("Y-m-d g:i:s a", 9223372036854793218) . "\n"; ?>

Output:

9223372036854775805: 292277026596-12-04 10:30:05 am
9223372036854775806: 292277026596-12-04 10:30:06 am
9223372036854775807: 292277026596-12-04 10:30:07 am (0x7FFFFFFFFFFFFFFF)
9223372036854775808: 292277026596-12-04 10:30:08 am
9223372036854775809: 292277026596-12-04 10:30:08 am
9223372036854775810: 292277026596-12-04 10:30:08 am
...
9223372036854778879: 292277026596-12-04 10:30:08 am
9223372036854778880: 292277026596-12-04 11:04:16 am
...
9223372036854778879: 292277026596-12-04 11:04:16 am
9223372036854778880: 292277026596-12-04 11:38:24 am
...
9223372036854780928: 292277026596-12-04 11:38:24 am
9223372036854780929: 292277026596-12-04 12:12:32 pm
...
9223372036854782975: 292277026596-12-04 12:12:32 pm
9223372036854782976: 292277026596-12-04 12:46:40 pm
...
9223372036854785024: 292277026596-12-04 12:46:40 pm
9223372036854785025: 292277026596-12-04 1:20:48 pm
...
9223372036854787071: 292277026596-12-04 1:20:48 pm
9223372036854787072: 292277026596-12-04 1:54:56 pm
...
9223372036854789120: 292277026596-12-04 1:54:56 pm
9223372036854789121: 292277026596-12-04 2:29:04 pm
...
9223372036854791167: 292277026596-12-04 2:29:04 pm
9223372036854791168: 292277026596-12-04 3:03:12 pm
...
9223372036854793215: 292277026596-12-04 3:03:12 pm
9223372036854793216: 292277026596-12-04 3:03:12 pm
9223372036854793217: -292277022657-01-27 8:37:04 am
9223372036854793218: -292277022657-01-27 8:37:04 am

---

So, the last reliable unix timecode is 9223372036854775808 (0x1000000000000000). Not that you would probably ever need a date that high.

[#30] Bas Vijfwinkel [2012-03-19 06:47:27]

Note that some formatting options are different from MySQL.
For example using a 24 hour notation without leading zeros is the option '%G' in PHP but '%k' in MySQL.
When using dynamically generated date formatting string, be careful to generate the correct options for either PHP or MySQL.

[#31] bakerj417 at gmail dot com [2012-03-07 16:48:48]

If you are having an issue getting u to work so is everyone else. The solution that I am using which I found on another site(so not taking credit) is to use this:

date("Y/m/d H:i:s"). substr((string)microtime(), 1, 6);

that will give you:

yyyy/mm/dd hh:ii:ss.uuuuuu

hope this helps someone in need!

thanks all

[#32] gerben at gerbenwijnja dot nl [2012-02-21 17:54:32]

I use the function below to calculate the Unix timestamp of the start of a week. It includes a boolean flag to request a GMT offset instead of the current locale setting.

<?php function getWeekOffsetTimestamp($year, $week, $useGmt = false) { if ($useGmt) { // Backup timezone and set to GMT $timezoneSettingBackup = date_default_timezone_get(); date_default_timezone_set("GMT"); } // According to ISO-8601, January 4th is always in week 1 $halfwayTheWeek = strtotime($year."0104 +".($week - 1)." weeks"); // Subtract days to Monday $dayOfTheWeek = date("N", $halfwayTheWeek); $daysToSubtract = $dayOfTheWeek - 1; // Calculate the week's timestamp $unixTimestamp = strtotime("-$daysToSubtract day", $halfwayTheWeek); if ($useGmt) { // Reset timezone to backup date_default_timezone_set($timezoneSettingBackup); } return $unixTimestamp; } ?>

[#33] frank at interactinet dot com [2012-02-15 22:07:14]

If you want to compare this week with the same week last year, here is some code to get you the time at the beginning of the week.  You can then add days, hours, etc to get to the day of the week that you want to know about.

<?php         $time_passed = (date('N')-1)* 24 * 3600; // time since start of week in days         $startOfWeek = mktime(0,0,0,date('m'),date('d'),date('Y')) - $time_passed;                       $lastyear = $startOfWeek - 365*24*3600;             // make sure time used from last year is the same week of the year             $weekdiff = date('W') - date('W',$lastyear);         if($weekdiff != 0)         {             $lastyear = $lastyear + ($weekdiff*7*24*3600);         }                  $lastyear_time_passed = (date('N',$lastyear)-1) * 24 * 3600; // time since start of week in days                  $startOfWeek_lastyear = mktime(0,0,0,date('m',$lastyear),date('d',$lastyear),date('Y',$lastyear)) - $lastyear_time_passed; ?>

So now you have the unix time for the start of this week ($startOfWeek), and the start of the same week last year ($startOfWeek_lastyear).

You can convert back to datetime format easily:

<?php         echo date('Y-m-d H:i:s',$startOfWeek).'<br>';         echo date('Y-m-d H:i:s',$startOfWeek_lastyear).'<br><br>';                  echo date('l F jS, Y',$startOfWeek).'<br>';         echo date('l F jS, Y',$startOfWeek_lastyear); ?>

[#34] Jimmy [2011-12-22 05:04:05]

Things to be aware of when using week numbers with years.

<?php echo date("YW", strtotime("2011-01-07")); // gives 201101 echo date("YW", strtotime("2011-12-31")); // gives 201152 echo date("YW", strtotime("2011-01-01")); // gives 201152 too ?>

BUT

<?php echo date("oW", strtotime("2011-01-07")); // gives 201101 echo date("oW", strtotime("2011-12-31")); // gives 201152 echo date("oW", strtotime("2011-01-01")); // gives 201052 (Year is different than previous example) ?>

Reason:
Y is year from the date
o is ISO-8601 year number
W is ISO-8601 week number of year

Conclusion:
if using 'W' for the week number use 'o' for the year.

[#35] blinov vyacheslav AT gmail.com [2011-08-23 07:06:51]

It was oblivious and discouraging that it dont mentioned in docs. If you will use W to get week number be aware:
first days of year can be in a week of previous year, and week number always has leading zero

<?php echo date("YW", strtotime("2011-01-07")); // gives 201101 echo date("YW", strtotime("2011-01-01")); // gives 201152 echo date("YW", strtotime("2011-12-31")); // gives 201152 too ?>

so you can`t rely on number of week given from this function inside your program if you want to use it for some logic

[#36] ghotinet [2010-12-13 10:06:29]

Most spreadsheet programs have a rather nice little built-in function called NETWORKDAYS to calculate the number of business days (i.e. Monday-Friday, excluding holidays) between any two given dates. I couldn't find a simple way to do that in PHP, so I threw this together. It replicates the functionality of OpenOffice's NETWORKDAYS function - you give it a start date, an end date, and an array of any holidays you want skipped, and it'll tell you the number of business days (inclusive of the start and end days!) between them.

I've tested it pretty strenuously but date arithmetic is complicated and there's always the possibility I missed something, so please feel free to check my math.

The function could certainly be made much more powerful, to allow you to set different days to be ignored (e.g. "skip all Fridays and Saturdays but include Sundays") or to set up dates that should always be skipped (e.g. "skip July 4th in any year, skip the first Monday in September in any year"). But that's a project for another time.

<?php function networkdays($s, $e, $holidays = array()) { // If the start and end dates are given in the wrong order, flip them. if ($s > $e) return networkdays($e, $s, $holidays); // Find the ISO-8601 day of the week for the two dates. $sd = date("N", $s); $ed = date("N", $e); // Find the number of weeks between the dates. $w = floor(($e - $s)/(86400*7)); # Divide the difference in the two times by seven days to get the number of weeks. if ($ed >= $sd) { $w--; } # If the end date falls on the same day of the week or a later day of the week than the start date, subtract a week. // Calculate net working days. $nwd = max(6 - $sd, 0); # If the start day is Saturday or Sunday, add zero, otherewise add six minus the weekday number. $nwd += min($ed, 5); # If the end day is Saturday or Sunday, add five, otherwise add the weekday number. $nwd += $w * 5; # Add five days for each week in between. // Iterate through the array of holidays. For each holiday between the start and end dates that isn't a Saturday or a Sunday, remove one day. foreach ($holidays as $h) { $h = strtotime($h); if ($h > $s && $h < $e && date("N", $h) < 6) $nwd--; } return $nwd; } $start = strtotime("1 January 2010"); $end = strtotime("13 December 2010"); // Add as many holidays as desired. $holidays = array(); $holidays[] = "4 July 2010"; // Falls on a Sunday; doesn't affect count $holidays[] = "6 September 2010"; // Falls on a Monday; reduces count by one echo networkdays($start, $end, $holidays); // Returns 246 ?>

Or, if you just want to know how many work days there are in any given year, here's a quick function for that one:

<?php function workdaysinyear($y) { $j1 = mktime(0,0,0,1,1,$y); if (date("L", $j1)) { if (date("N", $j1) == 6) return 260; elseif (date("N", $j1) == 5 or date("N", $j1) == 7) return 261; else return 262; } else { if (date("N", $j1) == 6 or date("N", $j1) == 7) return 260; else return 261; } } ?>

[#37] @PeteWilliams [2010-09-08 04:29:08]

If you want to use HTML5's <date> tag, the following code will generate the machine-readable value for the 'datetime' attribute:

<?php function getDateTimeValue( $intDate = null ) { $strFormat = 'Y-m-d\TH:i:s.uP'; $strDate = $intDate ? date( $strFormat, $intDate ) : date( $strFormat ) ; return $strDate; } echo getDateTimeValue(); ?>

[#38] lb at bostontech dot net [2009-11-29 23:11:05]

Not sure why this got ignored the first time, but this is an even simpler way to check leap year:

<?php function isLeapYear($year) { return ((($year%4==0) && ($year%100)) || $year%400==0) ? (true):(false); } ?>

[#39] Edward Rudd [2009-10-05 12:13:27]

To actually make use ot the "u" (microsecond) you need to use the DateTime object and not the date() function.

For example

<?php $t = microtime(true); $micro = sprintf("%06d",($t - floor($t)) * 1000000); $d = new DateTime( date('Y-m-d H:i:s.'.$micro,$t) ); print $d->format("Y-m-d H:i:s.u"); ?>

[#40] Just.Kevin [2009-07-28 09:52:48]

In order to determine if a year is a leap year an earlier poster suggested simply checking to see if the year is a multiple of four:

<?php function is_leapyear_broken($year = 2004) { return ($year%4)==0; } ?>

While this will work for the majority of years it will not work on years that are multiples of 100 but not multiples of 400 i.e.(2100).
A function not using php's date() function that will also account for this small anomaly in leap years:

<?php function is_leapyear_working($year = 2004) { if((($year%4==0) && ($year%100!=0)) || $year%400==0) { return true; } return false; } ?>

While is_leapyear_working will not return true for the few non-leap years divisible by four I couldn't tell you if this is more or less efficient than using php's date() as an even earlier poster suggested:

<?php function is_leapyear($year = 2004) { $is_leap = date('L', strtotime("$year-1-1")); return $is_leap; } ?>

[#41] eduardo at digmotor dot com dot br [2009-04-21 13:34:40]

Thanks to tcasparr at gmail dot com for the great idea (at least for me) ;)
I changed the code a little to replicate the functionality of date_parse_from_format, once I don't have PHP 5.3.0 yet. This might be useful for someone. Hope you don't mind changing your code tcasparr at gmail dot com.

<?php function dateParseFromFormat($stFormat, $stData) { $aDataRet = array(); $aPieces = split('[:/.\ \-]', $stFormat); $aDatePart = split('[:/.\ \-]', $stData); foreach($aPieces as $key=>$chPiece) { switch ($chPiece) { case 'd': case 'j': $aDataRet['day'] = $aDatePart[$key]; break; case 'F': case 'M': case 'm': case 'n': $aDataRet['month'] = $aDatePart[$key]; break; case 'o': case 'Y': case 'y': $aDataRet['year'] = $aDatePart[$key]; break; case 'g': case 'G': case 'h': case 'H': $aDataRet['hour'] = $aDatePart[$key]; break; case 'i': $aDataRet['minute'] = $aDatePart[$key]; break; case 's': $aDataRet['second'] = $aDatePart[$key]; break; } } return $aDataRet; } ?>

Also, if you need to change the format of dates:

<?php function changeDateFormat($stDate,$stFormatFrom,$stFormatTo) { // When PHP 5.3.0 becomes available to me //$date = date_parse_from_format($stFormatFrom,$stDate); //For now I use the function above $date = dateParseFromFormat($stFormatFrom,$stDate); return date($stFormatTo,mktime($date['hour'], $date['minute'], $date['second'], $date['month'], $date['day'], $date['year'])); } ?>

[#42] Anonymous [2008-09-12 06:01:56]

Correct format for a MySQL DATETIME column is
<?php $mysqltime = date ("Y-m-d H:i:s", $phptime); ?>

[#43] JonathanCross.com [2008-07-25 13:22:59]

<?php // A demonstration of the new DateTime class for those // trying to use dates before 1970 or after 2038. ?>
<h2>PHP 2038 date bug demo (php version <?php echo phpversion(); ?>)</h1>
<div style='float:left;margin-right:3em;'>
<h3>OLD Buggy date()</h3>
<?php   $format='F j, Y';   for ( $i = 1900; $i < 2050; $i++) {     $datep = "$i-01-01";     ?>
    Trying: <?php echo $datep; ?> = <?php echo date($format, strtotime($datep)); ?><br>
    <?php   } ?></div>
<div style='float:left;'>
  <h3>NEW DateTime Class (v 5.2+)</h3><?php   for ( $i = 1900; $i < 2050; $i++) {     $datep = "$i-01-01";     $date = new DateTime($datep);     ?>
    Trying: <?php echo $datep; ?> = <?php echo $date->format($format); ?><br>
    <?php   } ?></div>

[#44] chubby at chicks dot com [2008-05-23 06:54:43]

<?php function currentDayIsInInterval($begin = '',$end = '') { $preg_exp = '"[0-9][0-9][0-9][0-9]/[0-9][0-9]/[0-9][0-9]"'; $preg_error = 'Wrong parameter passed to function '.__FUNCTION__.' : Invalide date format. Please use YYYY/mm/dd.'; $interval_error = 'First parameter in '.__FUNCTION__.' should be smaller than second.'; if(empty($begin)) { $begin = 0; } else { if(preg_match($preg_exp,$begin)) { $begin = (int)str_replace('/','',$begin); } else { trigger_error($preg_error,E_USER_ERROR); } } if(empty($end)) { $end = 99999999; } else { if(preg_match($preg_exp,$end)) { $end = (int)str_replace('/','',$end); } else { trigger_error($preg_error,E_USER_ERROR); } } if($end < $begin) { trigger_error($interval_error,E_USER_WARNING); } $time = time(); $now = (int)(date('Y',$time).date('m',$time).date('j',$time)); if($now > $end or $now < $begin) { return false; } return true; } ?>

[#45] jc [2007-12-31 06:28:55]

date("W") returns the iso8601 week number, while date("Y") returns the _current_ year. This can lead to odd results. For example today (dec 31, 2007) it returns 1 for the week and of course 2007 for the year. This is not wrong in a strict sense because iso defines this week as the first of 2008 while we still have 2007.

So, if you don't have another way to safely retrieve the year according to the iso8061 week-date - strftime("%G") doesn't work on some systems -, you should be careful when working with date("W").

For most cases strftime("%W") should be a safe replacement.

[edit: Much easier is to use "o" (lower case O) instead of "Y"]

[#46] mel dot boyce at gmail dot com [2006-04-06 04:46:31]

I've been flicking through the comments looking for some succinct date code and have noticed an alarming number of questions and over-burdened examples related to date mathematics. One of the most useful skills you can utilize when performing date math is taking full advantage of the UNIX timestamp. The UNIX timestamp was built for this kind of work.

An example of this relates to a comment made by james at bandit-dot-co-dot-en-zed. James was looking for a way to calculate the number of days which have passed since a certain date. Rather than using mktime() and a loop, James can subtract the current timestamp from the timestamp of the date in question and divide that by the number of seconds in a day:
<?php $days = floor((time() - strtotime("01-Jan-2006"))/86400); print("$days days have passed.\n"); ?>

Another usage could find itself in a class submitted by Kyle M Hall which aids in the creation of timestamps from the recent past for use with MySQL. Rather than the looping and fine tuning of a date, Kyle can use the raw UNIX timestamps (this is untested code):
<?php $ago = 14; // days $timestamp = time() - ($ago * 86400); ?>

Hopefully these two examples of "UNIX-style" timestamp usage will help those finding date mathematics more elusive than it should be.

[#47] SpikeDaCruz [2006-03-09 11:12:16]

The following function will return the date (on the Gregorian calendar) for Orthodox Easter (Pascha).  Note that incorrect results will be returned for years less than 1601 or greater than 2399. This is because the Julian calendar (from which the Easter date is calculated) deviates from the Gregorian by one day for each century-year that is NOT a leap-year, i.e. the century is divisible by 4 but not by 10.  (In the old Julian reckoning, EVERY 4th year was a leap-year.)

This algorithm was first proposed by the mathematician/physicist Gauss.  Its complexity derives from the fact that the calculation is based on a combination of solar and lunar calendars.

<?php function getOrthodoxEaster($date){      $year = date("Y", $date);   $r1 = $year % 19;   $r2 = $year % 4;   $r3 = $year % 7;   $ra = 19 * $r1 + 16;   $r4 = $ra % 30;   $rb = 2 * $r2 + 4 * $r3 + 6 * $r4;   $r5 = $rb % 7;   $rc = $r4 + $r5;   //Orthodox Easter for this year will fall $rc days after April 3   return strtotime("3 April $year + $rc days"); } ?>