time: Parse does not detect bad days ("00" -> returns wrong date && err=nil)

[larsklingsten]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.7.3 darwin/amd64

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

OARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/larsklingsten/source/golang"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.7.3/libexec"
GOTOOLDIR="/usr/local/Cellar/go/1.7.3/libexec/pkg/tool/darwin_amd64"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/qc/2q_p2_zd32g_2lz3v5w8yclw0000gn/T/go-build111275672=/tmp/go-build -gno-record-gcc-switches -fno-co
mmon"
CXX="clang++"
CGO_ENABLED="1"

What did you do?

v, err := time.Parse("02.01.2006", "00.01.1970")
fmt.Println(v, err)

// see -> https://play.golang.org/p/FvCKKNbPK5

What did you expect to see?

0001-01-01 00:00:00 +0000 UTC

What did you see instead?

1969-12-31 00:00:00 +0000 UTC

[robpike]

Working as intended. As the docs say,

No checking is done that the day of the month is within the month's valid
dates; any one- or two-digit value is accepted. For example February 31 and
even February 99 are valid dates, specifying dates in March and May. This
behavior is consistent with time.Date.

[larsklingsten]

Thanks for very swift reply, appreciated.

Mentioned "31" and "99" for February does return "day out of range" error (as expected) . "00" instead overflows in the previous month with 'nil' error (unexpected)

(https://play.golang.org/p/o9lQ_TBTZH)

parse(...) DOES evaluate the validity of the day of the month.
...
// Validate the day of the month.
if day > daysIn(Month(month), year) {
return Time{}, &ParseError{alayout, avalue, "", value, ": day out of range"}
}

time.Parse("02.01.2006", "29.02.1970") -> returns "day out of range" error
time.Parse("02.01.2006", "00.01.1970") -> "1969-12-31 00:00:00 +0000 UTC"

This "00" overflowing from "00.01.1970" into "31.12.1969" with 'nil' error appears - to me - inconsistent.

[lucasalcantara]

Can I work on it?

[quentinmit]

@lucasalcantara Feel free to send a CL

[bradfitz]

@lucasalcantara, status?

Alternatively, anybody else (including @robpike) is welcome to send a CL.

[lucasalcantara]

@bradfitz sorry brad, my pc broke and will take a while to fix. So anyone can get this. I forgot to comment in here.

[odeke-em]

I can take this on, I've got the bandwidth and I've just prepared a CL for it, about to mail it.

[odeke-em]

Oops, the Gobot hadn't tagged this issue so I mailed a dupe CL https://go-review.googlesource.com/c/33434, @bradfitz's is ready to go, so I'll abandon mine :)