She found a perpetual calendar once and seems to have memorized it.

A perpetual calendar employs a table for finding which of fourteen yearly calendars to use.

Eventually, his work on calendars led to the invention of a perpetual or eternal calendar.

Up to five alarm calls per day can be set and there's a perpetual calendar as well.

I thumbed to the index and found the page numbers for a perpetual calendar.

We used to test him with a perpetual calendar and he was never wrong.

This is particularly advantageous where a watch has complications, such as perpetual calendars or moon phases.

"This is a perpetual calendar, it can show the date until the year 9999," he said.

With a seven-day week, we can have a perpetual calendar if each month has eight weeks.

I consulted the perpetual calendar we had on the shelf.