The seconds to calendar date conversion doesn't actually need to know about leap seconds.
At the seconds representation level, the same number is repeated twice (or the smearing trategy happens).
So the times before and after leap second get converted the the same date regardless of whether you know about the leap second or not. Edge case is that once second occuring twice. You might have seen that 23:59:60 seconds timestamp somewhere.
So the times before and after leap second get converted the the same date regardless of whether you know about the leap second or not. Edge case is that once second occuring twice. You might have seen that 23:59:60 seconds timestamp somewhere.