Chander Mases (चन्द्रमा माह) 

Tithi is based on Lunar/Chandra masas (month). : It starts from shukla pratipada (1st day of the bright half of the month which starts after the new Moon i.e. when the Moon crosses over the Sun and the difference between the two starts increasing from 0 degree Multurta Prakarana 31 onwards, say, 0.001) and ends at amavasya (the last day of the dark half of the month i.e. when the Sun and the Moon are together in a rashi exactly at the same degree). This mas relates to the Moon. The Hindi names of chandramas are:

1. Chaitra 2. Baisakh 3. Jyeshtha 4. Ashadh 5. Sravana  6. Bhadrapada 7. Ashwin 8. Kartika 9. Margashirsha 10 Pausha 11. Magha 12. Fahalgun

Saur mas सूर्य मास (Surya/Sun):

It relates to the Sun. It is the duration of Sun’s transit in one rashi (which starts from the time the Sun ingresses from Aries to Pises).

Nakshatra mas नक्षत्र मास :

It is the time taken by the Sun in transiting from (0° Aries) the start of Ashwini Nakshatra to the last degree of Revati (i.e. again coming on the point of start).