The Day of the Holy Innocents is also known as Childermas or Innocents’ Day, It is a Christian celebration in remembrance of the massacre of young children in Bethlehem by King Herod the Great in his attempt to kill the infant Jesus. Eastern churches observe this celebration on December 28 while Western churches do it on December 29. The slain children were regarded by the early Church as the first martyrs, but it is uncertain when the day was first kept as a Saint’s day. In Rome it was a day of fasting and mourning.

It was one of a series of days known as the Feast of Fools, and the last day of authority for boy bishops. Boy bishop was a name given to a custom very widespread in the Middle Ages, whereby a boy was chosen, for example among cathedral choristers, to parody the real bishop and parents temporarily abdicated authority. In convents and monasteries the youngest nuns and monks were allowed to act as abbess and abbot for the day. These customs were considered to mock religion and were condemned by the Council of Basel in 1431.

The day is still observed as a religious day and as a day of merrymaking for children.

In Mexico this day it is customary to make a friend innocent asking for something borrowed or making a joke and reminding the day with the verse Innocent dove you've been deceived, knowing that this day you should no one trust.