Konstantinos (Κωνσταντίνος)
Also: Constantine, Costas, Gus
Name day:
21 May
✓ sourced
Sources: namedays.gr / eortologio.gr online database (T2), OCA daily calendar (Slavic lineage — dates only, never name→feast) (T2)
Sts Constantine and Helen, Equals-to-the-Apostles. OCA 2026-05-21 + namedays.gr CONSTANTIN 21 May.
Sourced (✓) feasts are confirmed by two lineage-independent sources and are safe to put in a calendar. Unverified (⚠) feasts — whether resting on a single source or on a judgment call awaiting the printed synaxaria — are shown for reference but held out of feeds until confirmed.