name day (saint's day)
onomastici
o-no-MAS-ti-ko
Every day on the Italian Catholic calendar corresponds to a saint. If your name is that saint's name, it's your 'onomastico'. It used to be celebrated like a second birthday.
Oggi è il mio onomastico — mi chiamo Marco.
Today is my name day — my name is Marco.
Tanti auguri per il tuo onomastico!
Best wishes for your name day!