java获取时间戳单位秒,如何测试给定的时间戳是以秒或毫秒为单位？「建议收藏」

Assume a given variable, it is containing a UNIX time-stamp, but whether it is in seconds or milliseconds format is unknown, I want to assign to a variable which is in seconds format

For Example:

unknown = 1398494489444 # This is millisecond

t = ???

Updated: I understand it is not possible to tell without giving some limitations, so here is it

current_ts – 86400 * 365 < unknown < current_ts

Assume current_ts = current unix timestamp

解决方案

If you convert the maximum timestamp values with x digits in millis you get something like this:

9999999999999 (13 digits) means Sat Nov 20 2286 17:46:39 UTC

999999999999 (12 digits) means Sun Sep 09 2001 01:46:39 UTC

99999999999 (11 digits) means Sat Mar 03 1973 09:46:39 UTC

Can your timestamps be older than 2001? If not i think you’re safe to check whether the number has 13 digits or more – if yes you have milliseconds, if not you have seconds. Of course this will only work until timestamps in seconds will have 13 digits as well, which means timestamps in milliseconds will have 16 digits:

1000000000000000 (16 digits) means Fri Sep 27 33658 01:46:40 but by then i will be living on a planet from the Alpha Centauri system and time standards will probably have changed a bit :)

P.S. you can loosen up the condition to 12 digits or more, if your timestamps can’t go back further than 1973. The condition should only be ok up until:

100000000000000 (15 digits) means Wed Nov 16 5138 09:46:40

because this in seconds will have 12 digits and will overlap with your condition