Tatsuo Ishii <t-ishii(at)sra(dot)co(dot)jp> writes:
> How come 10 mons == 9 mons 30 days?
Because for purposes of comparisons, type interval assumes 1 month
== 30 days (cf. interval_cmp_internal). Pretty grotty, I agree,
but it's not easy to see how to do better.
regards, tom lane