[CentOS] lunar notation in crontab

ken
Sun, 06 Dec 2015 10:23:46 -0000

Crontab offers many refined facilities for Western calendaring, but none
for traditional Eastern-- lunar-- designations.  So for example, if one
wants specify regular occurring events on full moons or on new moons,
there is no way to do this.  Emacs (a text processor!?) accomplishes
this.  The math for calculating lunar calendaring is already available;
mathematical functions are already available for simple downloading and
so would need simply integration into crond.

User settings in crontab would make most sense designated in the 'day of
month' field with keyword either 'full' or 'new'
(abbreviated with 'f'
or 'n') prepended to a signed integer number of days (N * 24 hours).
I.e., "new+5" would specify '5 days after the new moon';
"full-1" would
specify "24 hours prior to the full moon"; "new+0",
"new-0" and "new"
would all mean the same: "the moment of the new moon".

I suppose that alternate syntaxes could be more refined, including hours
and minutes before/after new/full, so possibly useful, but then also
more complex.  Alternate and more refined time periods would be a
question for developers.