1
2difference : 2000 - 1999
3result     : -P1Y
4difference : 2000-01 - 1999-12
5result     : -P1M
6difference : 1999-12 - 2000-01
7result     : P1M
8difference : 1999-12-31 - 2000-01-01
9result     : P1D
10difference : 1999 - 2000-01
11result     : P1Y
12difference : 0002-01-05 - 0001-01-04
13result     : -P366D
14difference : 0002-05-05 - 0001-01
15result     : -P1Y4M
16difference : -0002-01-05 - 0001-01-04
17result     : P729D
18difference : 1970-01-01T05:04:03 - 1970-01-01T04:03:02
19result     : -PT1H1M1S
20difference : 2000-01-01T05:00:03 - 2000-01-01T04:03:02
21result     : -PT57M1S
22difference : 2000-01-01T05:00:03 - 1980-01-01T04:03:02
23result     : -P7305DT57M1S
24difference : 1970-01-01T04:03:02 - 1970-01-01T05:04:03
25result     : PT1H1M1S
26difference : 2000-01-01T04:03:02 - 2000-01-01T05:00:03
27result     : PT57M1S
28difference : 1980-01-01T04:03:02 - 2000-01-01T05:00:03
29result     : P7305DT57M1S
30difference : 2002-05-02T23:59:59 - 2002-05-03T00:00:01
31result     : PT2S
32difference : 2002-05-03T00:00:01 - 2002-05-02T23:59:59
33result     : -PT2S
34difference : 2000-01-02T05:00:03 - 2000-01-01T04:03:02
35result     : -P1DT57M1S