Software is often written with the assumption that time always goes forward, because, well, that's how time works. However, according to the rules of daylight savings, time actually goes backwards once a year.
This was resolved a long, long time ago - it's why we have a timezone file, so we can keep the system in GMT and have it convert user-interface stuff for the user.
Software is often written in ignorance of this fact - and causes headaches whenever things change.
Software is often written in ignorance of this fact - and causes headaches whenever things change.