Why golang time.Parse supports fractional seconds even the formatString does not have them?

Question

this code:

fmt.Println(time.Parse("2006-01-02T15:04:05", "2020-01-26T08:02:29.9"))

(https://go.dev/play/p/w1eZNdVgse4)

prints: 2020-01-26 08:02:29.9 +0000 UTC

It does not have fractional seconds in the format but they are still going though. Anyone any idea is there some reason to this. the source: https://cs.opensource.google/go/go/+/refs/tags/go1.18:src/time/format.go;l=1075;drc=refs%2Ftags%2Fgo1.18

user_11923999 · Answer

According to the documentation for time.Parse:

When parsing, if the seconds value is followed by a decimal point and some digits, that is taken as a fraction of a second even if the layout string does not represent the fractional second.

Why golang time.Parse supports fractional seconds even the formatString does not have them?

1 Answers