Samvatsara (संवत्सर) is a Sanskrit term for "year". In the Hindu calendar, there are 60 Samvatsaras, each of which has a name. Once all 60 samvatsaras are over, the cycle starts over again. On occasion, one will be skipped, as the count is based on the zodiac position of Jupiter, whose period around the Sun is slightly less than 12 years (the full cycle of 60 covers five Jovian years).
The sixty Samvatsaras are divided into 3 groups of 20 Samvatsaras each. The first 20 from Prabhava to Vyaya are assigned to Brahma. The next 20 from Sarvajit to Parabhava to Vishnu and the last 20 to Shiva.