[sqlite] determining is-leap-year in sqlite

[Eric Rubin-Smith]

>
>
>   select 2, 28 + (CAST(strftime("%j", c.year||"-12-31") AS INTEGER) % 365)
>

Here you assume that all years have either 365 or 366 days.  Would that it
were so!

Look at the year 1752 -- you may notice something odd happened that
September. :-)

Eric