As the documentation says, " RFC3339, RFC822, RFC822Z, RFC1123, and RFC1123Z are useful for formatting; when used with time.Parse they do not accept all the time formats permitted by the RFCs."

We can't change time.RFC3339 because that would break backward compatibility.

We aren't going to add a new constant just to use with time.Parse, because we already document that these constants don't do the right thing when used with time.Parse.

when used with time.Parse they do not accept all the time formats permitted by the RFCs

I hear your point, but the existing documentation says only that they don't accept all formats permitted. The docs don't say that they do accept formats prohibited by the RFCs, which is what I demonstrate.

If you don't want to change the existing constant (which I fully accept), or provide correct constants (which I question), what do you think about one or both of these:

• adding documentation to caveat that they accept prohibited formats
• providing an example of the stricter RFC3339 format (so that users can copy/paste it for use)

I'm happy to send a PR if we can agree in advance on what it should generally contain.

The title and description mention two digit "year". Is this intentional, or should it say "hour"?

Yes, thanks. Fixed the title.

I don't think it is possible to write a time format that works with time.Parse and that accepts exactly and only the time formats permitted by RFC 3339. The time.RFC3339 value produces a valid RFC 3339 time format when used with time.Time.Format. It does not and cannot work with time.Parse.

I'm fine with adding a clause saying that the various formats accept invalid strings when used with time.Parse. Maybe we can shorten the existing clause while we're at it.

Change https://golang.org/cl/229460 mentions this issue: time: note that formats may parse invalid strings