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. -zefram
