It was a Sunday.
If you mean what day of the week in 1951, then it would be a Sunday.
In the US, that fell on a Thursday.
28 January 1951 was on a Sunday.
January 30, 1951, was a Tuesday.
January 18, 1951 was a Thursday.
January 9, 1951 fell on a Tuesday.
January 9th, 1951 fell on a Tuesday.
January 1, 1951 fell on a Monday.
January 4, 1951 fell on a Thursday.
January 2nd, 1951 fell on a Tuesday.
January 19, 1951 fell on a Friday.