What is a perpetual calendar in a watch?

A perpetual calendar in a watch is designed to automatically adjust for the varying lengths of months and to account for leap years. This sophisticated mechanism means that the watch can accurately display the date without requiring manual corrections, even as it transitions between 30-day and 31-day months and incorporates February's 28 or 29 days in leap years.

This feature is highly regarded among watch enthusiasts because it reflects advanced engineering and horological mastery, allowing the wearer to have a continuously accurate representation of the date. Thus, selecting the option that defines a perpetual calendar as one that automatically adjusts for months and leap years correctly captures its fundamental function and purpose.