Remember that your code needs to account for the possibility of a negative leap second, meaning if you're using epoch time for timestamps you could have an instance that an event that happened after a previous one could be stamped as having happened before it instead.

https://en.wikipedia.org/wiki/Leap_second

Edit: Actually I was slightly wrong, in the event of a leap second, we would repeat the same second twice.

Thank you for the heads-up!

I try to write code loose enough that this would not be a problem. :)