cal 9 1752

If you type cal in linux terminal, it prints the calendar of the current month.

For fun type

cal 9 1752

It will print


From the linux man pages of cal - The Gregorian Reformation is assumed to have occurred in 1752 on the 3rd of September. By this time, most countries had recognized there formation(although a few did not recognize it until the early 1900's.) Ten days following that date were eliminated by the reformation, so the calendar for that month is a bit unusual.