Actually, Posix requires that leap seconds be ignored; see IEEE Std
1003.1b-1993 section 2.2.2.106 (page 22 lines 448-458). There is some
excellent doublespeak attempting to justify this in the annexes; my favorite
is ``it is inappropriate to require that a time represented as seconds since
the Epoch precisely represent the number of seconds between the referenced
time and the Epoch'' (section B.2.2.2 page 306 lines 620-622).
