Fatto generale: 30 is the number of days in the months April, June, September and November (and in unusual circumstances February).
Fatto matematico: 30 is the smallest sphenic number, and the smallest of the form where r is a prime greater than 3.
Trivia: 30 is the number of uprights that formed the Sarsen Circle at Stonehenge, also the supposed number of holes forming the arrays of Y and Z Holes at Stonehenge.
Data storica: January 30th is the day in 1972 that Pakistan withdraws from the Commonwealth of Nations.