[Guido]

There's a simpler reason for ignoring leap seconds in datetime: Python's wall clock is mappable to POSIX timestamps, which also ignore leap seconds (the reason being Tim's long explanation :-).

Ya, but I wanted to give some reasons that make actual sense ;-) Because when time wonks get agitated about this, it's just like American politics: both sides dig in and endlessly repeat the same talking points with ever-increasing volume. "Because POSIX said so" was smashed by the ever-affable Daniel Bernstein a long time ago: http://cr.yp.to/proto/utctai.html ... The main obstacle is POSIX. POSIX is a ``standard'' designed by a vendor consortium several years ago to eliminate progress and protect the installed base. The behavior of the broken localtime() libraries was documented and turned into a POSIX requirement. Fortunately, the POSIX rules are so outrageously dumb---for example, they require that 2100 be a leap year, contradicting the Gregorian calendar---that no self-respecting engineer would obey them. See? You've been paid off by vendors to eliminate progress, to protect their ill-gotten gains. datetime is just another tool of capitalist pigs to ensure they increase their profits at the expense of the people. Just thought I'd put that out there first ;-) boldly-speaking-truth-to-power-since-2015-ly y'rs - tmi