On Wed, Jul 31, 2013 at 11:09:22AM +0200, Marc Dahn wrote: > Dear list, > > Section 9.8 of the postgres (9.1) documentation says, on the > patterns for to_char(timestamp, pattern),: > > J Julian Day (days since November 24, 4714 BC at midnight) > > This leaves open the question of what's actually returned. At least > in astronomy, it is customary to have fractional days in JDs, whereas > postgres appears to always return an integer. Is that guaranteed > behaviour? > > The reason I'm asking is that I'd like to use the expression > > to_char($1, 'J')::double precision > + to_char($1,'ssss')::double_precision/86400 > - 2400001 > > to compute the modified julian date (MJD) from a postgres timestamp > in some software that may be around for longer. If postgres at some > point decided to return fractional days, that would blow up. > > > If integers are guaranteed, might I suggest to change the > documentation to read > > > J Chronological Julian Day (integer number of days since November 24, > 4714 BC at midnight) Done and backpatched to 9.3. I went with a simpler: Julian Day (integer days since November 24, 4714 BC at midnight) -- Bruce Momjian <bruce@xxxxxxxxxx> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
