Originally posted here by Katja
Nowadays, dates are stored differently. Often as a number of days since 1900 or since 1970. Thus the only limit now is the size of the number datatype (often 2 or 4 bytes) which won't cause many problems anymore for the next 50 years or so. (And then there will be a new Y2K like problem.) Storing dates as just a number of days used to be considered a slow method because it required the computer to do some serious calculations to translate it to day-month-year format. Nowadays computers are fast enough so this isn't a problem anymore.