Samvatsara – the year. Lunar year (Chandramana) und Solar year (Sauramana).
Ayana – half the year.
Masa – the month.
Paksha – the two phases of the moon.
Ritu – the season.
Ayana
The course of the sun to north (Uttarayana) and south (Dakshinayana).
Ritu/Masa
Shishira – Early spring, Magha, Phalguna – January/February, February/March.
Vasanta – Spring, Chaitra, Vaishaka – March/April, April/May.
Grishma – Summer, Jyeshtha, Ashadha – May/June, June/July.
Varsha – Rainy season, Shravana, Bhadrapada – July/August, August/September.
Sharada – Autumn, Ashvina, Karttika – September/October, October/November.
Hemanta – Winter, Margashirsa, Pausha – November/December, December/January.
Paksha
With Amavasya (new moon) Shuklapaksha, the bright, waxing phase of the moon begins.
With Purnima (full moon) Krishnapaksha, the dark, waning phase of the moon begins.
The cycle is Amavasya – Shuklapaksha – Purnima – Krishnapaksha.