why are people making such a drama of this - all Unix systems and those compatible don't even know that anything more than seconds exist. All of them count seconds from Jan 1 1970 and will completely be unaffected from a simple second being added to date names.
Well, date formatting will look wrong for an entire second, but that's about all the impact there is.
@wolfy1339(View Post) that isn't how leap seconds work, it is a UTC thing and already happened.
I have no idea how time zones handle it though, but the most correct way would be to add it at the UTC time, like for me it would have been at 7:59:60 PM