Monika’s name day is May 4, the feast of Monica, Mother of Augustine.
Churches that follow the Old (Julian) Calendar keep the same feast on May 17 of the civil calendar. See everything commemorated on May 4.
The saint behind the name
Monica, Mother of Augustine
May 4, Holy Woman, Μόνικα
Monica was born in North Africa in the fourth century to a Christian family and was given in marriage to a pagan husband, whom she eventually won to the faith by patience. She wept and prayed for many years for her gifted but wayward son Augustine.
Also celebrating on May 4
These names share the feast, many of them other forms of the same name:
What to say on a name day
The Greek wish is Χρόνια Πολλά (Chronia Polla), “many years.” A call or a short message on the day is what people remember. See name day wishes you can send and what a name day is.