On Mon, Nov 10, 2014 at 10:07 AM, Ilya Ashchepkov <koctep@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 ).