It was a Friday.
Monday
December 12 can fall on any day of the week.
15 December 1997 was a Monday.
December 25 1997 was a Thursday.
December 22, 1997, was a Monday.
Thursday, December, 25th, 1997.
December 5, 1997 was a Friday.
December 2, 1997 was a Tuesday.
December 19, 1997 fell on a Friday.
December 11, 1997 was a Thursday.
December 27, 1997 fell on a Saturday.
December 9, 1997 fell on a Tuesday.