Exported Constants

Constants are separated into groups by blank lines between each constant. Most constants have multiple individual export tags so you can use one that may be easier to remember.

I am happy to add new ones if you wish--just file an issue.

The last day the Julian calendar was used:

constant JCE is export(:JCE) = DateTime.new: :1582year, :10month, :4day;
constant jce is export(:jce) = JCE;

The official start date for the Gregorian calendar was October 15, 1582. The days of 5-14 were skipped (the 10 "lost days").

constant GC0 is export(:GC0) = DateTime.new: :1582year, :10month, :15day;
constant gc0 is export(:gc0) = GC0;

Posix0: Julian Date (JD) in the Gregorian calendar (1970-01-01T00:00:00Z)

constant POSIX0 is export(:POSIX0) = 2_440_587.5; 
constant posix0 is export(:posix0) = POSIX0;

MJD0: JD in Gregorian calendar (1858-11-17T00:00:00Z)

constant MJD0 is export(:MJD0) = 2_400_000.5; 
constant mjd0 is export(:mjd0) = MJD0;

Day constants

constant minutes-per-day is export(:minutes-per-day) = 1_440;
constant min-per-day     is export(:min-per-day)     = 1_440;

constant sec-per-day is export(:sec-per-day) = 86_400;
constant sec-per-cen is export(:sec-per-cen) = 3_155_760_000; 

A Julian century

constant days-per-jcen  is export(:days-per-jcen)  = 36_525; 
constant days-per-jcent is export(:days-per-jcent) = 36_525;        
constant days-per-cen   is export(:days-per-cen)   = 36_525;        

JD for 2000-01-01T12:00:00Z (astronomical epoch 2000.0)

constant J2000 is export(:J2000) = 2_451_545;    
constant j2000 is export(:j2000) = J2000;

JD for 1899-12-31T12:00:00Z (astronomical epoch 1900.0)

constant J1900 is export(:J1900) = 2_415_020;     
constant j1900 is export(:j1900) = J1900;

Difference between Sidereal and Solar hour (the former is shorter)

constant solar2sidereal is export(:solar2sidereal) = 1.002_737_909_350_795;