Mark H Weaver <m...@netris.org> writes: > Zefram <zef...@fysh.org> writes: > >> The date->string function from (srfi srfi-19), used on ISO 8601 formats >> "~1", "~4" and "~5", for years preceding AD 1, has an off-by-one error: >> >> scheme@(guile-user)> (use-modules (srfi srfi-19)) >> scheme@(guile-user)> (date->string (julian-day->date 0 0) "~4") >> $1 = "-4714-11-24T12:00:00Z" >> >> The date in question, the JD epoch, is 24 November 4714 BC (in the >> proleptic Gregorian calendar). In ISO 8601 format, that year is properly >> represented as "-4713", not "-4714", because ISO 8601 uses the AD era >> exclusively. 4714 BC = AD -4713. > > I agree that this is definitely a bug, but I'm nervous about deviating > from the SRFI-19 reference implementation, and therefore probably from > most other implementations of SRFI-19, in this way.
Also see my comments here: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=21904#17 which mention that ISO 8601 apparently requires that the sender and receiver agree ahead of time whether an extended format will be used, in which case a sign is *always* required, even when printing years in the range 0-9999. Mark
