short

Jan 1 of a year with $y mod 400 = 0$,
Jan 2 of a year with $y mod 400 = 0$,
...
Feb 28 of a year with $y mod 400 = 0$,
Feb 29 of a year with $y mod 400 = 0$,
Mar 1 of a year with $y mod 400 = 0$,
...
Dec 31 of a year with $y mod 400 = 0$,

Jan 1 of a year with $y mod 400 = 1$,
Jan 2 of a year with $y mod 400 = 1$,
...
Feb 28 of a year with $y mod 400 = 1$,
Mar 1 of a year with $y mod 400 = 1$,
...
Dec 31 of a year with $y mod 400 = 1$,

[Jan 1 to Dec 31 with no leap day] of a year with $y mod 400 = 2$,

[Jan 1 to Dec 31 with no leap day] of a year with $y mod 400 = 3$,

[Jan 1 to Dec 31 with a leap day] of a year with $y mod 400 = 4$,

...

[Jan 1 to Dec 31 with no leap day] of a year with $y mod 400 = 399$