time: time ParseInLocation error

[getaix]

Go version

go version go1.22.2 darwin/arm64

Output of go env in your module/workspace:

GO111MODULE='on'
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/abc/Library/Caches/go-build'
GOENV='/Users/abc/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/abc/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/abc/go'
GOPRIVATE=''
GOPROXY='https://goproxy.cn,direct'
GOROOT='/opt/homebrew/Cellar/go/1.22.2/libexec'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/opt/homebrew/Cellar/go/1.22.2/libexec/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.22.2'
GCCGO='gccgo'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/dev/null'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/h6/h_h0rdm91vgfb68pntxflth80000gp/T/go-build3222925675=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

s := "15/04/90 02:00"
fmt.Println(time.ParseInLocation("02/01/06 15:04", s, time.Local))
s = "15/04/90 03:00"
fmt.Println(time.ParseInLocation("02/01/06 15:04", s, time.Local))

What did you see happen?

➜ demo go run main.go
1990-04-15 03:00:00 +0900 CDT
1990-04-15 03:00:00 +0900 CDT

---

Both 15/04/90 02:00 and 15/04/90 03:00 are parsed as 1990-04-15 03:00:00

What did you expect to see?

➜ demo go run main.go
1990-04-15 02:00:00 +0900 CDT
1990-04-15 03:00:00 +0900 CDT

[ALTree]

Can you post a full, runnable program? Also what's time.Local on this machine? Or the value of the TZ env variable? This doesn't reproduce the issue:

package main

import (
	"fmt"
	"time"
)

func main() {
	loc, err := time.LoadLocation("America/Chicago")
	if err != nil {
		panic(err)
	}
	s := "15/04/90 02:00"
	fmt.Println(time.ParseInLocation("02/01/06 15:04", s, loc))
	s = "15/04/90 03:00"
	fmt.Println(time.ParseInLocation("02/01/06 15:04", s, loc))
}

1990-04-15 02:00:00 -0500 CDT
1990-04-15 03:00:00 -0500 CDT

[getaix]

loc, err := time.LoadLocation("Asia/Shanghai")
if err != nil {
    fmt.Println("Error loading location:", err)
    return
}

s := "15/04/90 02:00"
fmt.Println(time.ParseInLocation("02/01/06 15:04", s, loc))
s = "15/04/90 03:00"
fmt.Println(time.ParseInLocation("02/01/06 15:04", s, loc))

// output
1990-04-15 03:00:00 +0900 CDT
1990-04-15 03:00:00 +0900 CDT

[ALTree]

Oh, it's CDT as in China Daylight Time. There was a time change there on April 15 1990:

$ zdump -c 1989,1991 -v /usr/share/zoneinfo/Asia/Shanghai
[...]
/usr/share/zoneinfo/Asia/Shanghai  Sat Apr 14 17:59:59 1990 UT = Sun Apr 15 01:59:59 1990 CST isdst=0 gmtoff=28800
/usr/share/zoneinfo/Asia/Shanghai  Sat Apr 14 18:00:00 1990 UT = Sun Apr 15 03:00:00 1990 CDT isdst=1 gmtoff=32400
[...]

So 02:00 does not exists. From the documentation:

A daylight savings time transition skips or repeats times. For example, in the United States, March 13, 2011 2:15am never occurred, while November 6, 2011 1:15am occurred twice. In such cases, the choice of time zone, and therefore the time, is not well-defined. Date returns a time that is correct in one of the two zones involved in the transition, but it does not guarantee which.

Closing here as this is working as intended.