Ah, we have an extra day this year. Each time it reminds me of just how many people assume that these happen every four years, completely disregarding the rule or reason for these.
- Every year divisible by 4 is a leap year,
- of those years, if it is divisible by 100, it is NOT a leap year, unless
- the year is divisible by 400, in which case it IS a leap year.
The year 2000 was a leap year for this reason, as you can see… unless you apply all of the rules, your programatic date calculations may be incorrect in these cases.
While on the topic, there’s also the little known concept as a ‘leap second’, unless you are involved in communications or scientific applications you are probably not aware of this. Back when I was involved in submarine communications, we used to have to update our atomic (cesium beam) clocks to accomodate this irregularly planned change.
By the way, Happy Birthday to you ‘young ones’ born today!