time AddDate() Calculate time last month

[djxhhh]

Go version

go1.22.4 windows/amd64

Output of go env in your module/workspace:

set GO111MODULE=on
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Mayn\AppData\Local\go-build
set GOENV=C:\Users\Mayn\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\Mayn\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\Mayn\go
set GOPRIVATE=
set GOPROXY=https://goproxy.cn,direct
set GOROOT=C:/Program Files/Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLCHAIN=auto
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.22.4
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=0
set GOMOD=D:\gamecomponents\go.mod
set GOWORK=
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -fno-caret-diagnostics -Qunused-arguments -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=C:\Users\Mayn\AppData\Local\Temp\go-build4203366999=/tmp/go-build -gno-record-gcc-switches

What did you do?

func main() {
date := time.Date(2023, 12, 31, 0, 0, 0, 0, time.UTC)
lastMonth := date.AddDate(0, -1, 0)
fmt.Println("last year last month time:", lastMonth.Format("2006-01-02"))
now := time.Now().UTC()
nowLastMonth := now.AddDate(0, -1, 0)
fmt.Println("now last month time:", nowLastMonth.Format("2006-01-02"))
}

What did you see happen?

out: last year last month time: 2023-12-01
now last month time: 2024-12-01

What did you expect to see?

out: last year last month time: 2023-11-30
now last month time: 2024-11-30

I can achieve the effect myself through other methods, but I hope the standard package can fix this problem. I want to know if this problem has been fixed in other versions. If it has been fixed, please let me know the corresponding version.

[gabyhelp]

Related Issues

• time.AddDate() can't get Feb #31130 (closed)
• golang `time.AddDate` operation incorrect #65397 (closed)
• affected/package: time #63843 (closed)
• time: Wrong `time.AddDate` calculation if months' last date is 31 #57139 (closed)
• time: AddDate with negative day changed behavior #68718 (closed)
• time AddDate(0, -1, 0) does not work for March. #31145 (closed)
• 20201231 user time.AddDate(0,-1,0), result is 20201201 #43457 (closed)
• AddDate return error result #20155 (closed)
• time: i find some problems when using addDate to do date calculation #66374 (closed)

Related Discussions

• time.Now().AddDate(0,-1,0) result confusing.

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[djxhhh]

I think that for the operation of getting last month, I should give me the data of last month, right? Now that the method month is valid, the last month and this month must have the same current date? Then I think the month parameter is a bit confusing.

[seankhliao]

you get Nov 31, which is normalized to Dec 1.
this is also described in the docs for the function.
closing as working as intended.