time: cannot parse GMT timezones with colon-separated offsets

[DanielHeath]

go version
go version go1.4 linux/amd64

uname -a
Linux daniel-linux 3.16.0-28-generic #38-Ubuntu SMP Fri Dec 12 17:37:40 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

This program shows my attempt to parse the time: http://play.golang.org/p/2-YXz2wdIx

I've traced it to src/time/format.go, which consumes any integers following the letters GMT.

The minutes (after the colon) then cause a parse failure.

Because the letters GMT are treated specially, I don't think it's possible to parse this time with the time package.

[robpike]

I apologize for not picking up this issue earlier, but it is now too late to fix for the 1.5 release: it would be unwise to change the internals of time.Parse and time.Format at this late date. I will mark it to be addressed early in the 1.6 release cycle.

[robpike]

Unfortunate. The special handling of GMT, which is needed for other things, makes it very difficult to know whether the :10:00 should be considered part of the time zone or left alone to match the layout.

[katzien]

A workaround I used in my project, in case anyone finds it useful - https://play.golang.org/p/EshUUdz-fz

in1 := "Mon, 4 Jul 2016 16:13:17 +0830 (GMT+08:30)"
in2 := "Mon, 4 Jul 2016 16:13:17 -0500 (GMT-0500)"

regGMTTimezone := regexp.MustCompile(`(?i)GMT([+-]\d{2}:?\d{2}]?)`)

out1 := regGMTTimezone.ReplaceAllString(in1, "$1")
out2 := regGMTTimezone.ReplaceAllString(in2, "$1")

fmt.Println(out1)
fmt.Println(out2)

f1 := "Mon, 2 Jan 2006 15:04:05 -0700 (-07:00)"
f2 := "Mon, 2 Jan 2006 15:04:05 -0700 (-0700)"

if t1, err := time.Parse(f1, out1); err == nil {
    fmt.Println(t1.UTC().Format(time.RFC822))
}
if t2, err := time.Parse(f2, out2); err == nil {
    fmt.Println(t2.UTC().Format(time.RFC822))
}

outputs:

Mon, 4 Jul 2016 16:13:17 +0830 (+08:30)
Mon, 4 Jul 2016 16:13:17 -0500 (-0500)
04 Jul 16 07:43 UTC
04 Jul 16 21:13 UTC

The regex will only affect timezones given in GMT, it won't affect say "UTC+08:00".