get, manipulate and convert dates and times in scheme.

uses a proleptic gregorian calendar with negative years and a year 0 equivalent to 1 BCE

iso8601 and the gnu date utility include a year zero as well, to which the output is compatible.

international atomic time is used because it does not use leap seconds. with utc it is

not predictable when future leap seconds will be inserted, which makes it impossible to calculate accurate future times with utc.

the implementation does not depend on other time libraries, only on a function that gives the current utc posixtime.

it might also contain useful examples for calendar and time calculation implementors.

objects

  utc: integer: utc seconds since the unix epoch. utc uses leap seconds to conform to (= number-of-days (/ utc-seconds 86400))

  tai: integer: tai seconds since the unix epoch. as elapsed, no leap seconds

  date: vector: gregorian calendar date, daytime and timezone offset