The 300th anniversary of an event.

A 300-year period.

300 वर्षों की अवधि।

English Usage: The tricentennial of the establishment of the colony was marked by festive events.

Hindi Usage: कॉलोनी की स्थापना की त्रिशताब्दी को उत्सवी आयोजनों द्वारा मनाया गया।