The Parse documentation says:

When parsing a time with a zone abbreviation like MST, if the zone abbreviation has a defined offset in the current location, then that offset is used.

and

If the zone abbreviation is unknown, Parse records the time as being in a fabricated location with the given zone abbreviation and a zero offset

and

To avoid such problems, prefer time layouts that use a numeric zone offset, or use ParseInLocation

So you can either use the numeric offset, or call ParseInLocation:

loc, _ := time.LoadLocation("US/Pacific")
const longForm = "Jan 2, 2006 at 15:04 (MST)"
t, _ := time.ParseInLocation(longForm, "Feb 3, 2013 at 19:30 (PST)", loc)
fmt.Println(t)

2013-02-03 19:30:00 -0800 PST

I guess in the documentation it recognizes PST as -08 because it's the godoc tz?

Which timezones are recognized depends on the timezone database on your computer.

Timezone names are inherently ambiguous and should be avoided when possible for portability.

Closing because I don't think there is anything to do. Please comment if you disagree.

@ianlancetaylor @ALTree

That explanation makes sense. I did not realise the timezone database is on my computer, hence I found the disparity between my setup and play.golang.org weird.

Thank you