A calendar that can be used perpetually or over a wide range of years. That of Capt. Herschel covers, as given below, dates from 1750 to 1961 only, but is capable of indefinite extension.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). perpetual calendar. Retrieved September 29, 2026, from http://smartdefine.org/perpetual_calendar/definitions/2044082 |
| Chicago | Webster's. 2011. "perpetual calendar" http://smartdefine.org/perpetual_calendar/definitions/2044082 (accessed September 29, 2026). |
| Harvard | Webster's 2011, perpetual calendar, Smart Define, viewed 29 September, 2026, <http://smartdefine.org/perpetual_calendar/definitions/2044082>. |
| MLA | Webster's. "perpetual calendar" 27 May 2011. Web. 29 September 2026. <http://smartdefine.org/perpetual_calendar/definitions/2044082> |