Even though many have hoped that the authorities would stop fiddling with our clocks, today a leap second will be inserted in UTC. Systems using Olson/IANA timezone database have a way to deal with this without adjusting their clocks, but few systems are configured that way: $ TZ=right/UTC date -d @1341100824 Sat Jun 30 23:59:60 UTC 2012 (1341100824 is the number of seconds since epoch including the leap seconds.) Python's time module works fine with the "right" timezones:
import time print(time.strftime('%T', time.localtime(1341100824))) 23:59:60
but the datetime module clips the leap second down to the previous second:
from datetime import datetime from datetime import datetime print(datetime.fromtimestamp(1341100824).strftime('%T')) 23:59:59 print datetime.fromtimestamp(1341100823).strftime('%T') 23:59:59
BDFL has been resisting adding support for leap seconds to the datetime module [1], but as the clocks become more accurate and synchronization requirements become stricter, we may want to revisit this issue. [1] http://mail.python.org/pipermail/python-ideas/2010-June/007307.html