First i was like why is there even a question like this
After reading this
Exactly
To elaborate, systems that assume Unix timestamps are always sequential will be mistaken about the ordering of events that take place during a leap second and the following second, since the two seconds are indistinguishable from the timestamps. For example, an event which occurs at 11:59:60.8 PM will have a later timestamp than an event that takes places half a second later at 12:00:00.3 AM, since 11:59:60 PM and 12:00:00 AM are the same in Unix time. (And some systems, when dealing with human-readable time formats, will give an error on seeing the 60.8 seconds, since such a timestamp is "obviously" invalid.)
Bitcoin has none of these problems. It does not use timestamps to determine the ordering of events, with out-of-order timestamps being perfectly valid, and a single second will not make any appreciable difference to the block interval.
