A lot of online time calculators don't properly account for leap seconds. For example, http://billionbirthday.com/ http://billionbirthday.com/ doesn't (of cours

A lot of online time calculators don't properly account for leap seconds. For example, http://billionbirthday.com/ http://billionbirthday.com/ doesn't (of course, it can't account for yet-to-be-announced leap seconds, but it could include currently known leap-seconds). Wolfram Alpha doesn't seem to either (at least, it doesn't have the most recent leap second). I only know this because I work on a balloon experiment and some of the quantities our GPS reports are not in UTC Time (so don't have leap second corrections).