Date conversion code behaving different on different machines

Question

I have the below code:

package main

import (
    "fmt"
    "time"
)

func main() {
    loc := "Jan 06"
    date := "2020-12-31 16:00:00 +0000 UTC"
    layout := "2006-01-02 15:04:05 -0700 MST"
    t, err := time.Parse(layout, date)
    if err != nil {
        fmt.Print("Error")
    }

    fmt.Println(t)
    GetFormattedDate(t, loc)
}

func GetFormattedDate(date time.Time, layout string) (string, error) {
    
    fmt.Println("\n\n====================================================")
    fmt.Println("time.Now(): ", time.Now())
    fmt.Println("time.Now().Location(): ", time.Now().Location())
    fmt.Println("Converting: ", date)
    configLocale := "Singapore"
    fmt.Println("configLocale: ", configLocale)

    loc, err := time.LoadLocation(configLocale)
    fmt.Println("loc: ", loc)
    if err != nil {
        return "", err
    }

    date = date.In(loc)
    fmt.Println("date.In(loc): ", date)
    fmt.Println("layout: ", layout)
    converted := fmt.Sprintf(date.Format(layout))
    fmt.Println("converted fmt: ", converted)
    fmt.Println("\n\n==================================================")
    return fmt.Sprintf(date.Format(layout)), nil
}

When I run it locally I get:

====================================================
time.Now():  2009-11-10 23:00:00 +0000 UTC m=+0.000000001
time.Now().Location():  Local
Converting:  2020-12-31 16:00:00 +0000 UTC
configLocale:  Singapore
loc:  Singapore
date.In(loc):  2021-01-01 00:00:00 +0800 +08 // This is the issue
layout:  Jan 06
converted fmt:  Jan 21


==================================================

But when I run the same code on my linux box server, I get:

time.Now(): 2020-10-24 09:04:22.256288497 +0000 UTC m=+252.011109438
time.Now().Location(): UTC
Converting: 2020-12-31 16:00:00 +0000 UTC
msg":"configLocale: Singapore
msg":"loc: Singapore
date.In(loc): 2020-12-31 16:00:00 +0000 +0000 // This is the issue
layout: Jan 06
converted fmt: Dec 20

What I am trying to do:

I am trying to convert: 2020-12-31 16:00:00 +0000 UTC into a locale specific date, locale being Singapore. My layout is Jan 06

For one machine this date converts to Dec 20 and for another it converts to Jan 21

Specifically when I dig deeper, I feel the method date = date.In(loc) returns different result on different machines despite setting location to Singapore and passing it explicitly, as is evident in the logs.

Playground

However on the server commandline:

/ # zdump Singapore 
Singapore  Mon Oct 26 02:10:18 2020 +08

Any suggestions how do I solve this issue?

Answer 1

It is the value of configLocale. It needs to be an IANA Time Zone, "", "UTC", or "Local". "Singapore" is in the list, however it is one of the very few that doesn't follow the standard format of Continent/Region. It is an unusual format, so the lookup on the server machine fails the lookup and thus defaults to UTC (without returning an error, which may be a bug), and since Singapore is 8 hours ahead, you end up off by 8 hours. If you use "Asia/Singapore" for configLocale it will work.