Auto calendar on a watch ends after the year 2029 or 2099. How could the watch be used after that year?

Many of our watches have an "auto calendar" feature, which enables the watch to show the correct day of the week that corresponds to a particular year, month, and day setting. The watch is preprogrammed with a certain time frame, e.g. from 1980 to 2029, or from 2000 to 2099.

After that time frame ends, you could still use the watch, but you would have to set the calendar to a year that matches the arrangement for whatever year that you are in. For example, to obtain a calendar similar to the year 2030, you could set the year on your watch to 1991 or 2002. Or, to obtain a calendar similar to the year 2100, you could set the year on your watch to 2021 or 2094. See the following link for more information:

https://www.timeanddate.com/calendar/repeating.html