Lunation or Thidhi has been defined as
Lunation ( Thidhi) = Longitude of Moon – Longitude of Sun.
From 0 to 12 degrees is Prathama and from 12 to 24 degrees is Dwitheeya and so on. It becomes easy to find out which Tidhi the time falls on. We give the degrees and the nomenclature of the Thidhis or Lunation.
12PRATHAMA 1
24DWITHEEYA 2
36THRITHEEYA 3
48CHATHURTHI 4
60PANCHAMI 5
72SHASHTI 6
84SAPTHAMI 7
96ASHTAMI 8
108NAVAMI 9
120DASAMI 10
132EKADASI 11
144DWADASI 12
156THRAYODASI 13
168CHATHURDASI 14
180POURNAMI 15
192PRATHAMA 16
204DWITHEEYA 17
216THRITHEEYA 18
228CHATHURTHI 19
240PANCHAMI 20
252SHASHTI 21
264SAPTHAMI 22
276ASHTAMI 23
288NAVAMI 24
300DASAMI 25
312EKADASI 26
324DWADASI 27
336THRAYODASI 28
348CHATHURDASI 29
360AMAVASYA 30