time: regression in Format

[dsymonds]

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

go version devel +cd97aca3fd Mon Jan 1 03:45:23 2018 +0000 darwin/amd64

Does this issue reproduce with the latest release?

play.golang.org (currently go1.9.2) does not show this issue.

What did you do?

See https://play.golang.org/p/1VcPUlPk_3. Here's the relevant part:

t := time.Date(2016, 8, 18, 16, 31, 33, 0, time.UTC)
fmt.Println(t.Format("20060102_1504"))

In previous versions of Go, and in the playground, it produces 20160818_1631. In my dev version, it produces 20160818 83331.

[dsymonds]

I just updated to tip, and it looks like it was already fixed.

[dsymonds]

Yep, 8776be1 broke it and 86cca11 fixed it.

[mvdan]

For completeness sake, this is a dup of #23259.