On Mon, Nov 10, 2014 at 10:07 AM, Ilya Ashchepkov <koc...@gmail.com> wrote:
> Is this correct? > $ select > justify_interval(t-f-i) > ,t-f-i > from > ( > select > timestamp '2014-1-1' as f, > timestamp '2015-1-1' as t, > interval '06:49:00' as i > ) S; > > justify_interval | ?column? > ------------------------+-------------------- > 1 year 4 days 17:11:00 | 365 days -06:49:00 > > Why do we have 360 days in a year? > > Seems to be, the docs says: justify_days(interval) interval Adjust interval so 30-day time periods are represented as months justify_days(interval '35 days') 1 mon 5 days justify_hours(interval) interval Adjust interval so 24-hour time periods are represented as days justify_hours(interval '27 hours') 1 day 03:00:00 justify_interval(interval) interval Adjust interval using justify_days and justify_hours, with additional sign adjustments justify_interval(interval '1 mon -1 hour') 29 days 23:00:00 And, IIRC, an interval stores 3 parts, months, days and secods. The 365 days are justified to 12 months 5 days by justify days, then the 5 days - 6:49:0 are justified to 4 days 17:11:00 and then the 12 months are printed as 1 year ( because months are printed as MM/12 years, MM%12 months ). What I'm not sure is why the right column is stated as 365 days minus six hours and change instead of 1 year minus six hours, maybe testing the parts in sequence may shed light on it, but I wouldn't rely on justify_xxx for any precise thing on big intervals given it's definition ( unless you are working only with intervals and using 30 days months, 24 hour days exclusively ). Francisco Olarte.
