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time: system TZ is UTC, but time.Local != time.UTC #9832

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pbnjay opened this issue Feb 10, 2015 · 6 comments

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@pbnjay
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commented Feb 10, 2015

This was a very unexpected bug, considering all output and other logging statements matched up.

$ cat tt.go

package main

import (
    "fmt"
    "time"
)

func main() {
    t1 := time.Now()
    t2 := t1.UTC()
    fmt.Println(t1, " == ", t2, " => ", t1==t2)
}

$ go run tt.go

2015-02-10 19:51:15.366942319 +0000 UTC  ==  2015-02-10 19:51:15.366942319 +0000 UTC  =>  false

go version devel +2d02ff2 Sat Dec 13 10:18:27 2014 +0000 linux/amd64

@DisposaBlackSwan

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commented Feb 10, 2015

It wasn't clear whether or not you're aware of http://golang.org/pkg/time/#Time.Equal. I'm not sure t == t is ever what one wants.

@ianlancetaylor

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commented Feb 10, 2015

See the note about == at http://golang.org/pkg/time/#Time .

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commented Feb 10, 2015

TBH I was using time.Time as map keys when I stumbled on this, so I couldn't use Time.Equal anyways.

The code above was just a minimal test case, since even when trying to debug this the output matched exactly. I had to dig all the way into zoneinfo_unix.go to see that they weren't the same value.

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commented Feb 10, 2015

@ianlancetaylor I've seen the note, but it's not clear that Local = "UTC" and UTC = "UTC" are different things. Obviously bugs/docs are up to y'all, at least now if someone else has the issue they'll be able to google this particular edge case. Cheers

@nightlyone

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commented Feb 10, 2015

@pbnjay please note, that you actually CAN use times as map keys, if you call .UTC() before storing them, since t1.UTC() == t2.UTC() => true, iff t1.Equal(t2) => true

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commented Feb 10, 2015

yeah that's what I'm doing now.... but again, docs make it unclear that I
have to force .UTC() even when it's already in UTC.

Jeremy

On Tue, Feb 10, 2015 at 4:22 PM, Ingo Oeser notifications@github.com
wrote:

@pbnjay https://github.com/pbnjay please note, that you actually CAN
use times as map keys, if you call .UTC() before storing them, since
t1.UTC() == t2.UTC() => true, iff t1.Equal(t2) => true


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#9832 (comment).

@mikioh mikioh changed the title system TZ is UTC, but time.Local != time.UTC time: system TZ is UTC, but time.Local != time.UTC Feb 10, 2015

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