The dates for this name (Gusztáv) are:
Gusztáv etymology - what does Gusztáv mean?
See here for a
complete list of
Hungarian name days (magyar névnapok),
detailing today's nameday.
Name days are a tradition of attaching personal names to each day of the year,
and celebrating the association of particular days with those for whom that day is named.
The tradition originates from the Christian church calendar and the tradition to name children after saints.
From Wikipedia.
Name days are like a second birthday in Hungary.
A woman is typically given flowers on her name day by friends, even colleagues.
A suitable greeting is boldog névnapot kívánok (neked)!
I wish you a happy name-day!