time: Truncate() not truncating as expected for non-UTC times.

[c9845]

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

$ go version 1.19 windows/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

$ go env
set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\USER\AppData\Local\go-build
set GOENV=C:\Users\USER\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\USER\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\USER\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\Program Files\Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.19
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=go.mod
set GOWORK=
set CGO_CFLAGS=-g -O2
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-g -O2
set CGO_FFLAGS=-g -O2
set CGO_LDFLAGS=-g -O2
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=C:\Users\USER\AppData\Local\Temp\go-build3387395096=/tmp/go-build -gno-record-gcc-switches

What did you do?

I am located in the America/New_York time zone. I am using time.Truncate().

What did you expect to see?

time.Now().Truncate(24 * time.Hour) should output "2022-09-28 00:00:00 -0400 EDT".

What did you see instead?

time.Now().Truncate(24 * time.Hour) instead outputs "2022-09-28 20:00:00 -0400 EDT". Note the extra "20" hours.

[c9845]

See also:
https://stackoverflow.com/questions/36988681/time-time-round-to-day

[seankhliao]

Truncate operates on the time as an absolute duration since the zero time

Closing as working as intended (and documented)

[c9845]

What is the suggested alternative for getting a non-UTC YYYY-MM-DD time.Time? Is doing time.Now().Format("2006-01-02") and then a time.Parse()` really the best option?

[ianlancetaylor]

time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, 0, t.Location())

For further questions please don't use the issue tracker, please see https://go.dev/wiki/Questions. Thanks.