JavaScript convert world time

With the acceleration of globalization, communication and cooperation across time zones have gradually become the norm. In this process, an in-depth understanding of the principles and methods of time conversion in the JavaScript world is an essential skill. In this article, we will focus on how to perform world time conversion in JavaScript, allowing you to easily master this skill.

1. The concept of world time in JavaScript
World time refers to the standard time used uniformly internationally. Because the earth is divided into 24 time zones, and the time in each time zone is different, in order to facilitate communication and unify business operations, the international community adopted Coordinated Universal Time (UTC) as the world standard time in 1986. UTC uses the Greenwich Observatory as its origin and adds one to the time every hour, so UTC is 8 hours behind most time zones in the world.

In JavaScript, the world time can be obtained through the built-in Date object, and the world time can be converted by calling the corresponding function.

2. Convert JavaScript world time to local time
When we need to use world time for operations, we often need to convert world time to local time. The specific operation method is as follows:

var utcTime = new Date("2019-12-31T10:30:00Z"); // utc time
var localTime = new Date(utcTime.getTime() utcTime.getTimezoneOffset() 60 1000); //Convert to local time

Explain the above code:

1. First, we create a UTC time object, represented as new Date("2019-12-31T10:30:00Z "). Note that when expressing UTC time, you need to add "Z" at the end of the time string.
2. Then, get the difference (in minutes) between the current time zone and the UTC time zone through utcTime.getTimezoneOffset(). getTimezoneOffset() returns the number of minutes that the current time zone is different from UTC, so you also need Multiply by 60*1000 to convert to milliseconds.
3. Finally, use localTime = new Date(utcTime.getTime() utcTime.getTimezoneOffset() 60 1000) to convert UTC time to local time.

It should be noted that the difference obtained by getTimezoneOffset() is a positive or negative integer. If the system time zone is earlier than UTC time, the result of the subtraction is a positive number, otherwise it is a negative number. .

3. Convert JavaScript local time to world time
When you need to convert local time to world time, you can also achieve the conversion in a similar way:

var localTime = new Date(" 2019-12-31T10:30:00"); // Local time
var utcTime = new Date(localTime.getTime() - localTime.getTimezoneOffset() 60 1000); // Convert to UTC time

Explain the above code:

1. First, we create a local time object, represented as new Date("2019-12-31T10:30:00").
2. Then, use localTime.getTimezoneOffset() to obtain the difference (in minutes) between the current time zone and the UTC time zone. You also need to multiply the result by 60*1000 to convert it into milliseconds.
3. Finally, use utcTime = new Date(localTime.getTime() - localTime.getTimezoneOffset() 60 1000) to convert the local time to UTC time.

It should be noted that the difference obtained is a positive or negative integer, so the addition and subtraction operations here need to be performed according to the specific situation.

4. Formatting time in JavaScript
In actual development, we often need to format time into a specific string for better reading or transmission to other systems. In JavaScript, you can format time by calling the method of the Date object and using formatting syntax.

The following are some commonly used formatting syntax and uses:

%d: represents the day of the month (01–31)

%m: represents the month (01–31) 12)

%Y: Indicates the year

%H: Indicates the hour (00-23)

%M: Indicates the minute

%S: Indicates Seconds

%w: Indicates the day of the week (0-6)

%a: Indicates the abbreviation of the day of the week (Mon-Fri)

Usage is as follows:

var now = new Date();
var dateString = now.toLocaleString('chinese', { hour12: false }); // Convert to local time
console.log(dateString); / / 2022/12/24 19:26:28

In the above code, we specify the language type as chinese by calling the toLocaleString() function of the Date object, and turn on the 24-hour clock (the hour12 parameter is set to false ), and finally returns a formatted date string.

5. Conclusion
With the rapid development of the Internet, world time conversion has become an indispensable part of daily work and scientific research. This article focuses on the principles and methods of world time conversion in JavaScript, including common operations such as converting world time to local time, converting local time to world time, and time formatting. I hope it will be helpful to readers.

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