general_fact: 30 is the number of days in the months April, June, September and November (and in unusual circumstances February).
math_fact: 30 is the sum of the first four squares, which makes it a square pyramidal number.
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.
historical_date: January 30th is the day in 1960 that the African National Party is founded in Chad, through the merger of traditionalist parties.