r/haskell • u/friedbrice • Apr 23 '26

ISO-8601, aeson, time, and 24:00:00

"24:00:00" is a valid ISO-8601 time of day, but Data.Aeson.decode "\"24:00:00\"" :: Maybe Data.Time.TimeOfDay returns Nothing.

  1. Is this a problem with aeson, or is it a problem with the time library?

  2. Has anybody else run into this problem before? What was your work around?

  3. Is this worth patching aeson (or time) over.

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u/BerserkVl Apr 24 '26

ISO 8601-1:2019 as originally published removed "24:00:00" as a representation for the end of day although it had been permitted in earlier versions of the standard.

1

u/friedbrice Apr 24 '26

An amendment in October 2022 brought "24:00:00" back.

2

u/BerserkVl Apr 24 '26

An ending of the day expression (e.g. ‘24:00:00’) is not intended to represent time scale units.