~9 min read
Encyclopedic overview
February 31 on a tombstone Several non-standard dates are used in calendars for various purposes: some are expressly fictional, some are intended to produce a rhetorical effect (such as sarcasm), and others attempt to address a particular mathematical, scientific or accounting requirement or discrepancy within the calendar system.
Historical
Excerpted from Wikipedia’s “March 0” article, available under the CC BY-SA 4.0 licence.