Partial order on durations: P1M <> P30D P1M =< P32D P3M =< P92D P1Y >= PT31535000S P11M =< P1Y P12M == P1Y P1D == PT24H PT1S =< PT1M1S PT1S =< PT1.0001S -PT1S >= -PT1.0001S Adding durations to date-times: 1901-12-31 00:00:00 + P1D = 1902-01-01 00:00:00 1901-12-31 00:00:00 + P1M = 1902-01-31 00:00:00 1901-12-31 00:00:00 + P1Y = 1902-12-31 00:00:00 1901-12-31 00:00:00 + PT1H = 1901-12-31 01:00:00 1901-12-31 00:00:00 + PT1M = 1901-12-31 00:01:00 1901-12-31 00:00:00 + PT1S = 1901-12-31 00:00:01 2000-02-28 00:00:00 + P1D = 2000-02-29 00:00:00 2001-01-30 00:00:00 + P1M = 2001-02-28 00:00:00 2000-01-30 00:00:00 + P1M = 2000-02-29 00:00:00 2007-01-01 00:00:00 + PT31536000S = 2008-01-01 00:00:00 2008-01-01 00:00:00 + PT31536000S = 2008-12-31 00:00:00 2008-03-31 00:00:00 + -P1M = 2008-02-29 00:00:00 2007-03-31 00:00:00 + -P1M = 2007-02-28 00:00:00 1000-01-01 00:00:00 + -PT1M = 0999-12-31 23:59:00 2000-03-01 00:00:00 + -PT1H = 2000-02-29 23:00:00 -0001-01-01 00:00:00 + -PT1S = -0002-12-31 23:59:59 -0001-01-01 00:00:00.123 + -PT1.123S = -0002-12-31 23:59:59 2009-02-28 23:59:59.99 + PT0.01S = 2009-03-01 00:00:00 2009-02-28 23:59:59.99 + P1MT0.02S = 2009-03-29 00:00:00.01 Computing durations: G: 2008-01-01 00:00:00 -> 2200-04-04 04:04:04 = P192Y3M3DT4H4M4S checked ok G: 2200-04-04 04:04:04 -> 2008-01-01 00:00:00 = -P192Y3M3DT4H4M4S checked ok D: 2008-01-01 00:00:00 -> 2200-04-04 04:04:04 = P70220DT4H4M4S checked ok D: 2200-04-04 04:04:04 -> 2008-01-01 00:00:00 = -P70220DT4H4M4S checked ok G: 2008-01-31 00:00:00 -> 2008-02-29 10:00:00 = P1MT10H checked ok G: 2008-02-29 10:00:00 -> 2008-01-31 00:00:00 = -P29DT10H checked ok D: 2008-01-31 00:00:00 -> 2008-02-29 10:00:00 = P29DT10H checked ok D: 2008-02-29 10:00:00 -> 2008-01-31 00:00:00 = -P29DT10H checked ok G: 2000-01-31 00:00:00 -> 2001-01-29 00:00:00 = P11M29D checked ok G: 2001-01-29 00:00:00 -> 2000-01-31 00:00:00 = -P11M29D checked ok D: 2000-01-31 00:00:00 -> 2001-01-29 00:00:00 = P364D checked ok D: 2001-01-29 00:00:00 -> 2000-01-31 00:00:00 = -P364D checked ok G: 2000-02-29 00:00:00 -> 2001-01-31 00:00:00 = P11M2D checked ok G: 2001-01-31 00:00:00 -> 2000-02-29 00:00:00 = -P11M checked ok D: 2000-02-29 00:00:00 -> 2001-01-31 00:00:00 = P337D checked ok D: 2001-01-31 00:00:00 -> 2000-02-29 00:00:00 = -P337D checked ok G: 2000-02-29 22:58:58 -> 2001-01-31 23:59:59 = P11M2DT1H1M1S checked ok G: 2001-01-31 23:59:59 -> 2000-02-29 22:58:58 = -P11MT1H1M1S checked ok D: 2000-02-29 22:58:58 -> 2001-01-31 23:59:59 = P337DT1H1M1S checked ok D: 2001-01-31 23:59:59 -> 2000-02-29 22:58:58 = -P337DT1H1M1S checked ok G: 2001-02-28 00:00:00 -> 2001-03-29 00:00:00 = P1M1D checked ok G: 2001-03-29 00:00:00 -> 2001-02-28 00:00:00 = -P1M checked ok D: 2001-02-28 00:00:00 -> 2001-03-29 00:00:00 = P29D checked ok D: 2001-03-29 00:00:00 -> 2001-02-28 00:00:00 = -P29D checked ok G: 2001-02-27 00:00:00 -> 2001-03-29 00:00:00 = P1M2D checked ok G: 2001-03-29 00:00:00 -> 2001-02-27 00:00:00 = -P1M1D checked ok D: 2001-02-27 00:00:00 -> 2001-03-29 00:00:00 = P30D checked ok D: 2001-03-29 00:00:00 -> 2001-02-27 00:00:00 = -P30D checked ok G: 1975-06-05 12:00:00 -> 1977-10-09 12:00:00 = P2Y4M4D checked ok G: 1977-10-09 12:00:00 -> 1975-06-05 12:00:00 = -P2Y4M4D checked ok D: 1975-06-05 12:00:00 -> 1977-10-09 12:00:00 = P857D checked ok D: 1977-10-09 12:00:00 -> 1975-06-05 12:00:00 = -P857D checked ok G: 1977-10-09 12:00:00 -> 1980-01-05 11:11:11 = P2Y2M26DT23H11M11S checked ok G: 1980-01-05 11:11:11 -> 1977-10-09 12:00:00 = -P2Y2M26DT23H11M11S checked ok D: 1977-10-09 12:00:00 -> 1980-01-05 11:11:11 = P817DT23H11M11S checked ok D: 1980-01-05 11:11:11 -> 1977-10-09 12:00:00 = -P817DT23H11M11S checked ok G: 1977-10-09 12:00:00 -> 1980-03-01 12:00:00 = P2Y4M21D checked ok G: 1980-03-01 12:00:00 -> 1977-10-09 12:00:00 = -P2Y4M23D checked ok D: 1977-10-09 12:00:00 -> 1980-03-01 12:00:00 = P874D checked ok D: 1980-03-01 12:00:00 -> 1977-10-09 12:00:00 = -P874D checked ok G: 1977-10-09 12:00:00 -> 1980-03-01 13:01:01.000007 = P2Y4M21DT1H1M1.000007S checked ok G: 1980-03-01 13:01:01.000007 -> 1977-10-09 12:00:00 = -P2Y4M23DT1H1M1.000007S checked ok D: 1977-10-09 12:00:00 -> 1980-03-01 13:01:01.000007 = P874DT1H1M1.000007S checked ok D: 1980-03-01 13:01:01.000007 -> 1977-10-09 12:00:00 = -P874DT1H1M1.000007S checked ok Day of the week: 2008-01-15 23:59:00 : tuesday 2008-01-16 19:08:00 : wednesday 1360-04-14 00:00:00 : monday 1865-02-27 00:00:00 : monday 1886-02-08 00:00:00 : monday 1929-10-28 00:00:00 : monday 0000-12-31 00:00:00 : sunday 0001-01-01 00:00:00 : monday -0001-12-31 00:00:00 : friday 0000-01-01 00:00:00 : saturday Parse test: P2Y6M100DT10H16M30.0003S Month-to-int (1-based): january -> 1 february -> 2 march -> 3 april -> 4 may -> 5 june -> 6 july -> 7 august -> 8 september -> 9 october -> 10 november -> 11 december -> 12 Month-to-int (0-based): january -> 0 february -> 1 march -> 2 april -> 3 may -> 4 june -> 5 july -> 6 august -> 7 september -> 8 october -> 9 november -> 10 december -> 11 Int-to-month (1-based): -1 -> out-of-range 0 -> out-of-range 1 -> january 2 -> february 3 -> march 4 -> april 5 -> may 6 -> june 7 -> july 8 -> august 9 -> september 10 -> october 11 -> november 12 -> december 13 -> out-of-range Int-to-month (0-based): -1 -> out-of-range 0 -> january 1 -> february 2 -> march 3 -> april 4 -> may 5 -> june 6 -> july 7 -> august 8 -> september 9 -> october 10 -> november 11 -> december 12 -> out-of-range 13 -> out-of-range Same date: 2014-12-04 12:53:00 == 2014-12-04 12:53:00 2014-12-04 12:53:00 == 2014-12-04 12:54:00 2014-12-04 12:53:00 != 2014-12-05 12:53:00 2014-12-04 12:54:00 != 2014-12-05 12:53:00