time: ParseInLocation error

[FreeDemon]

What version of Go are you using (go version)?

$ go version
go version go1.17.2 darwin/amd64

What operating system and processor architecture are you using (go env)?

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/freedemon/Library/Caches/go-build"
GOENV="/Users/freedemon/Library/Application Support/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="/Users/freedemon/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="darwin"
GOPATH="/Users/freedemon/go"
GOPRIVATE=""
GOPROXY="https://goproxy.cn"
GOROOT="/usr/local/Cellar/go/1.17.2/libexec"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.17.2/libexec/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.17.2"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="/Users/freedemon/Documents/code/goProject/go2/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/9y/nkxhf5yd3c7fvqdsdvdwm18r0000gn/T/go-build2346662675=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Why are these times incorrect and missed some time ?

package main

import (
	"fmt"
	"time"
)

func main() {
	timeLayout := "2006-01-02 15:04:05"
	loc, _ := time.LoadLocation("Asia/Shanghai")

	time1, _ := time.ParseInLocation(timeLayout,"1991-09-14 16:50:50", loc)
	fmt.Println(time1)

	time2, _ := time.ParseInLocation(timeLayout,"1991-09-14 17:00:00", loc)
	fmt.Println(time2)

	time3, _ := time.ParseInLocation(timeLayout,"1991-09-15 00:50:00", loc)
	fmt.Println(time3)

	time4, _ := time.ParseInLocation(timeLayout,"1991-09-15 01:00:00", loc)
	fmt.Println(time4)
}

What did you expect to see?

1991-09-14 16:50:50 +0900 CDT
1991-09-14 17:00:00 +0900 CDT
1991-09-15 00:50:00 +0900 CDT
1991-09-15 01:00:00 +0800 CST

What did you see instead?

1991-09-14 16:50:50 +0900 CDT
1991-09-14 18:00:00 +0900 CDT
1991-09-15 01:50:00 +0900 CDT
1991-09-15 01:00:00 +0800 CST

[ALTree]

This does seem a bug.

In absence of a timezone indicator, ParseInLocation should interpret the timestamp as if it was in the given location. Asia/Shanghai did end Daylight Saving Time at 02:00, Sep 15 1991, but 1991-09-14 17:00:00 is several hours before that. Why is it corrected to 18:00 ?

cc @ianlancetaylor

[gopherbot]

Change https://golang.org/cl/360616 mentions this issue: time: fix looking for zone offset when date is close to a zone transition

[rchunping]

seems a bug
use this instead:

loc:= time.FixedZone("Asia/Shanghai",3600*8)

[FreeDemon]

seems a bug use this instead:

loc:= time.FixedZone("Asia/Shanghai",3600*8)

thank u, i'll try it

[zhouguangyuan0718]

seems a bug use this instead:
loc:= time.FixedZone("Asia/Shanghai",3600*8)

thank u, i'll try it

The actual time between 1991-04-14 02:00:00 to 1991-09-15 01:00:00 in Asia/Shanghai is Daylight Saving Time. We can't use fixed offset for it.

This bugs happens because it get an incorrect offset in the function time.Data:

go/src/time/time.go

Line 1444 in bd580a0

_, offset, _, _, _ = loc.lookup(start - 1)

At that time. the start is invalid, we can't get the correctly offset by lookup(start-1).

@FreeDemon You can try the CL above. I think It can solve this problem.
#49284 (comment)

[zhouguangyuan0718]

@gopherbot please open backport to 1.16 and 1.17

[gopherbot]

Backport issue(s) opened: #49406 (for 1.16), #49407 (for 1.17).

Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://golang.org/wiki/MinorReleases.