Why doesn't time.ParseDuration() support days?

[EdSchouten]

Prometheus has a command line flag storage.local.retention that can be used to configure the retention period of metrics. It looks like this string is parsed using time.ParseDuration().

Right now it has a default value of 15 days (360h0m0s), but in my specific case I want to set it to some higher value, say one year. This means that I need to specify 8784h, which looks quite unreadable.

I can understand why Duration can't support concepts like months and years, due to their irregular length. That said, would it make sense to extend it to support days? That way you could simply specify 366d instead.

[ianlancetaylor]

In most locations days also have an irregular length. There is one 23 hour day and one 25 hour day per year. Since there is no clear way to resolve the ambiguity, we force the program to decide how it wants to handle it.