Dates and times can be represented in Antik with the
timepoint class. A timepoint is a specific point in Newtonian time, so includes a date and time, and a timescale (best thought of as a timezone). Timepoints are most conveniently made with the #d reader macro; the default timescale is UTC, and the standard format for specification of timepoints is
ANTIK-USER> #d2011-08-04T12:00 2011-08-04 12:00:00.000 #d2011-08-04T12:00EST 2011-08-04 17:00:00.000
Other timescales available are
GPS, and any of the customary
time zone abbreviations that define offsets from UTC; these are listed in the variable
In order to convert to and from UT1, it is necessary to obtain earth orientation parameters from the US Naval Observatory; if *real-ut1-utc* is
nil, then UT1 is taken the same as UTC.
read-time will read a timepoint or time interval in ISO8601 format. Timepoints may be read in any format using the function
read-timepoint. The default is the ISO8601 format, with a broadened allowance for separators between the components. A day without a specific time will be marked :day-only. The function
read-us-date is provided to read US-style dates (month/day/year).
ANTIK-USER> (read-time "2011-08-04T12:00") 2011-08-04 12:00:00.000 ANTIK-USER> (read-time "1999?03/30 % 12-33-45") 1999-03-30 12:33:45.000 ANTIK-USER> (read-timepoint "20/12/2011" '(2 1 0)) ; Read a European-style date 2011-12-20 ANTIK-USER> (read-us-date "12/20/2000 3:41:12") 2000-12-20 03:41:12.000 ANTIK-USER> (read-us-date "12/20/11 3:41:12") ; Two-digit years are acceptable 2011-12-20 03:41:12.000
Dates are output in ISO8601 format. The function
write-us-date can be used to format in US style.
Specification of a point in time, including a scale.
Read a timepoint from a string with specification for the position in the string of each component; pos-ymdhms is a list of year, month, day, hour, minute, and second as sequence numbers for the integers in the string. Scale is the timescale (zone) as a string or symbol. If pos-ymdhms has only three components, or only a date is provided, the timepoint created will be specifed as day-only. The default reads an