Friday
It was a Thursday.
13th October 1981 was a Tuesday.
the 13th
September 13th, 1981 fell on a Sunday.
Sunday
It was a Friday.
Thursday
Monday
It was a Friday.
August 13th 1981 was a Thursday.
Februray 13th, 1970 fell on a Friday.
May 13th, 1981 fell on a Wednesday. The following year, it fell on a Thursday.