cal - print calendar
cal [ month ] [ year ]
Cal prints a calendar. Month is either a number from 1 to 12, a lower case month name, or a lower case three-letter prefix of a month name. Year can be between 1 and 9999. If either month or year is omitted, the current month or year is used. If only one argument is given, and it is a number larger than 12, a calendar for all twelve months of the given year is produced; otherwise a calendar for just one month is printed. The calendar produced is that for England and her colonies.
cal sep 1752
The year is always considered to start in January even though this is historically naive.
Beware that refers to the early Christian era, not the 20th century.