Why Does My Go Code Always Return UTC Time Despite Specifying Different Time Zones Using `time.Parse`?

Parsing Timezone Codes: A Deeper Dive

In a previous attempt to parse timezone codes, the code below consistently yielded the result "[date] 05:00:00 0000 UTC" regardless of the timezone chosen for the parseAndPrint function.

// time testing with arbitrary format
package main

import (
    "fmt"
    "time"
)

func main() {
    now := time.Now()
    parseAndPrint(now, "BRT")
    parseAndPrint(now, "EDT")
    parseAndPrint(now, "UTC")
}

func parseAndPrint(now time.Time, timezone string) {
    test, err := time.Parse("15:04:05 MST", fmt.Sprintf("05:00:00 %s", timezone))
    if err != nil {
        fmt.Println(err)
        return
    }

    test = time.Date(
        now.Year(),
        now.Month(),
        now.Day(),
        test.Hour(),
        test.Minute(),
        test.Second(),
        test.Nanosecond(),
        test.Location(),
    )

    fmt.Println(test.UTC())
}

This issue stems from the fact that time.Parse interprets the time in the current location, which may not match the intended timezone.

Resolving the Problem: Understanding Timezone Context

To accurately parse timezone codes, the correct approach involves using time.Location. Here's an improved implementation:

func parseAndPrint(now time.Time, timezone string) {
    location, err := time.LoadLocation(timezone)
    if err != nil {
        fmt.Println(err)
        return
    }

    test, err := time.ParseInLocation("15:04:05 MST", "05:00:00", location)
    if err != nil {
        fmt.Println(err)
        return
    }

    fmt.Println(test.UTC())
}

In this updated code:

• time.LoadLocation(timezone) loads the specified timezone location.
• time.ParseInLocation("15:04:05 MST", "05:00:00", location) parses the time "05:00:00" in the specified timezone location. This yields the correct time in the intended timezone.

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