The interesting thing there is that these problems of wall-clock time have largely been solved at every level other than seconds. Years vary in length - 365 or

The interesting thing there is that these problems of wall-clock time have largely been solved at every level other than seconds. Years vary in length - 365 or 366 days. It's 29th February. Add one year. Is it 28th February or 1st March? What if it's 28th February or 1st March now, but next year is a leap year? Months vary in length - 28, 29, 30 or 31 days. It's 31st March. Add one month. What is the date? 30th April or 1st May? What if it's 30th March? Is your "add one month" function strictly increasing? We KNOW that days vary in length - 23, 24 or 25 hours. It's 00:59 and the clocks go forward today. Add two minutes. What time is it? 01:01 or 02:01? It's 01:59 and the clocks go back today. Add two minutes. Is it 01:01 or 02:01? Now we simply have a situation where a minute can also vary in length - 59, 60 or 61 seconds. It's 23:59:58. Add 2 seconds. Is it 00:00:02, 00:00:00 or 23:59:60? These problems are not difficult. The same approaches can be applied to each one. The only difficulty is awareness. Leap seconds are rarer and less predictable than Daylight Saving, month boundaries or even leap years. But Daylight Saving isn't predictable either - the rules change all the time. Just solve it with tables.