++ed by:
Author image Tom Wyant
and 1 contributors


usno-seasons - Compare equinox and solstice calculations to those of the U. S. Naval Observatory


 usno-seasons 2001
 usno-seasons -help
 usno-seasons -version



This option displays the documentation for this script. The script then exits.


This option displays the version of this script. The script then exits.


This Perl script calculates the equinoxes and solstices for the year given on the command line (defaulting to the current year) and compares them to the calculations of the United States Naval Observatory. The USNO data are obtained via its API. Because the USNO restricts its API to the years 1700 through 2100, this script has the same restriction.

For each season three lines of output are produced. The first is the year and the name of the season, the latter as provided by Astro::Coord::ECI::Sun. The second is the date/time and ecliptic longitude of the season, as calculated by Astro::Coord::ECI::Sun. The third is the date/time returned from the U. S. Naval Observatory, and the ecliptic longitude calculated by Astro::Coord::ECI::Sun for that time.

Note that the U. S. Naval Observatory only gives the times to the nearest minute. We arbitrarily set the seconds to 0 when interpreting USNO times.

This script assumes the U. S. Naval Observatory's API returns the seasons in order by the time they occur. If this assumption is wrong, the USNO data will show up at the wrong place in the output.


Tom Wyant (wyant at cpan dot org)


Copyright (C) 2018-2021 by Thomas R. Wyant, III

This program is free software; you can redistribute it and/or modify it under the same terms as Perl 5.10.0. For more details, see the full text of the licenses in the directory LICENSES.

This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.