What day of the week was December 21, 1361?

The day of the week December 21st, 1361 fell on was a Monday.

There were 4 days until Christmas.

The Battle of Linuesa is fought in the context of the Spanish Reconquista between the forces of the Emirate of Granada and the combined army of the Kingdom of Castile and of Jaén resulting in a Castilian victory.