Peter Zilahy Ingerman, PhD, FBCS - Consultants

We specialize in Computer, Human, and Systems Symbiosis...
making all of the parts work together simply and smoothly for the benefit of all the parts!

February 30th!

February 30th

Found in American Scientist - A Letter To the Editors:

In “The Future of Time,” the authors state that “different countries and religions adopted the reforms [the Gregorian calendar] at different times and in different ways. In 1712 Sweden added a February 30 to its national calendar.” There was a February 30 in Sweden in 1712, but the context in which it is presented in the article is misleading. In 1700 the Swedes decided to switch from the Julian to the Gregorian calendar by eliminating leap-year days for 40 years. So 1700, which is a Julian leap year but not a Gregorian leap year, did not have a leap day. In both 1704 and 1708, through bureaucratic error, there were leap days. In 1712, the situation was resolved by switching back to the Julian calendar; this meant that the missing leap day that would have occurred in 1700 had to be added, and was, as February 30. It wasn’t until 1753 that the Swedes finally adopted the Gregorian calendar by making the date March 1 follow February 17.

by Peter Zilahy Ingerman

The above quote can be found online:
American Scientist - Date Distinctions

The article referred to can be found at:

A more in depth explanation about February 30th can be found on:

  • There are claims that the Soviet revolutionary calendar had a February 30th from 1930-1931, but careful research has not found any records of it being put into practice or used such that a February 30th actually occurred.
  • There are also claims that in the Julian calendar February had 30 days in leap years between 45 BC and 8 BC, but these have yet to be proven.
  • There were also many who felt February 2000 should have had a 30th day! For more about this see:
  • There is, however, a February 30 in In J.R.R. Tolkien's Middle-earth legendarium... though the month is properly called "Solmath".

If you like correlating dates across calendar systems Peter Ingerman wrote a program that does just that! It is called Megacal.
It is fairly comprehensive in the calendar systems included. It is equally comprehensive in including the holiday systems (both civic and religious) in use in many countries currently and historically, as well as including lots of other useful and obscure calendar related data!

For more about the program, Megacal, see: