Demystifying The Tamil Calendar – Thidhis and Festivals


Continued from Part 1

Thidhi – How to track anniversaries?

Leaving aside technical calculations, we can understand generally that the 14 days between every Amavasya and Pournami, and vice-versa, are divided into 14 thidhis. They are as follows:

  1. Pradamai (First day after Amavasya/Pournami)
  2. Dvithiai (Second day after Amavasya/Pournami)
  3. Trithiai (Third day after Amavasya/Pournami)
  4. Chaturthi (Fourth day after Amavasya/Pournami)
  5. Panchami (Fifth day after Amavasya/Pournami)
  6. Shashti (Sixth day after Amavasya/Pournami)
  7. Sapthami (Seventh day after Amavasya/Pournami)
  8. Ashtami (Eighth day after Amavasya/Pournami)
  9. Navami (Nineth day after Amavasya/Pournami)
  10. Dasami (Tenth day after Amavasya/Pournami)
  11. Ekadasi (Eleventh day after Amavasya/Pournami)
  12. Dvadasi (Twelfth day after Amavasya/Pournami)
  13. Triyodasi (Thirteenth day after Amavasya/Pournami)
  14. Chaturdasi (Fourteenth day after Amavasya/Pournami)

The period from Amavasya to Pournami is referred to as Valar Pirai or Shukla Paksham. ‘Valar’ roughly translates ‘to grow’. It indicates that during the period the moon ‘grows’ in size.

The period from Pournami to Amavasya is refered to as Thei Pirai or Krishna Paksam. ‘Thei’ roughly translates to ‘erode’ in tamil. It indicates that during the period the moon diminishes in size.

To arrive on a date based on thidhi, we need the month, the paksham or the pirai, and the thidhi. For eg., Akshaya Trithiai is celebrated every year on ‘Panguni month’, ‘Valar Pirai or Shukla Paksham’ and ‘Trithiai’ thidhi.

Srardhams (death anniversaries) are marked on the basis of thidhi and not on the basis of star. Thus while for calculating the birthdays we use month and star, for calculating death anniversaries we use thidhis.

Special Days

A few days of the month that are considered special are as follows:




Sankatahara Chaturthi Chaturthi of Thei Pirai every month. Lord Ganesha is worshiped on this day.
Pradosham Triyodasi – twice every month [The period when Dvadasi ends and Triyodasi begins]. Lord Siva and Parvathi are worshiped on this day. If it falls on a Saturday, it is called Sani Pradosham.
Sivarathri Generally, the night of Chaturdasi during Thei Pirai every month. Lord Siva is worshiped on this day. If Chaturdasi lasts for less than 6 hours during the night, the previous night i.e., the night of Triyodasi, is marked as Sivarathri.


Some common festivals are marked as below:




Pongal/Sankranthi 1st day of Thai month
Ratha Sapthami Thai/Maasi – Valar Pirai – Sapthami Sapthami after Thai Amavasya
Bhisma Ekadasi Thai/Maasi – Valar Pirai – Ekadasi Ekadasi after Thai Amavasya. Considered to be the day on which Bhisma revealed Vishnu Sahasranama Stotram to the Pandavas
Maha Sivarathri Maasi – Sivarathri Sivarathri in the month of Maasi
Karadayan Nombhu 1st day of Panguni month Festival similar to Karva Chauth where married women fast for well-being of their husbands, and unmarried women seek blessings for a suitable groom
Ramanavami Panguni/Chithirai -Valar Pirai-Navami Valar Pirai Navami after Panguni Amavasya. Considered to be the birthday of Lord Rama.
Tamil New Year 1st day of Chitirai month
Akshaya Trithiai Chitirai-Valar Pirai-Trithiai Considered to be the birthday of Lord Parsurama, and the day on which Veda Vyasa and Lord Ganesha began writing Mahabharata. It is considered auspicious to buy gold on this day.
Sankara Jayanthi Chitirai/Vaigasi-Valar Pirai-Panchami Valar Pirai Panchami after Chitirai Amavasya. Considered to be the birthday of Adi Sankara.
Chitra Pournami Pournami of Chitirai month Considered to be the birthday of Chitraguptan.
Mahalayam Starts from Purataasi Pournami, ends on the next Amavasya called the Mahalaya Amavasya It is believed that one’s forefathers come to down to earth during the period.
Navarathri Starts from the day after Mahalaya Amavasya
Saraswathi Puja Navami Thidhi of Navarathri
Dussera/Vijaya Dasami Dasami Thidhi of Navarathri Vijaya Dasami marks the slaying of Mahishasura by Goddess Durga. Also considered to be the day when Lord Rama killed Ravana. The day is considered to be auspicious for starting a new venture or business or commercial activity.
Diwali First Amavasya after Dussera Considered to be the day when Lord Rama and Sita return to Ayodhya after van-vaas. It is also celebrated as the day on which the demon Narakasura was slayed by Lord Krishna and Satyabhama.
Vaikunta Ekadasi Margazhi-Valar Pirai-Ekadasi Considered to be the auspicious day when ‘Vaikunta Dwaram’ is opened for devotees.
Koodaravalli 27th day of Margazhi It is considered that after 27 days, Andal’s fast came to an end on this day. The only thing I know about this day is ‘Akkaravadisal’ is prepared and served on this day!

The above are only a few of our main festivals. There are many not included here because I haven’t yet understood them. I will try to keep updating as many as I can. Meanwhile, if you find anything here needs correction, please feel free to let me know.

As mentioned earlier, the above post is only for beginners like me who have no understanding of what the Tamil calendar is about. Hence, the information here is mostly simplified and devoid of technicalities. Should one look deeper, one would find that everything is based on a lot of technical calculations. For those interested in knowing more, there are a plenty of material available online.

Hoping that this post would have given you some basic introduction to the fundamentals of the Tamil calendar!

Categories: Life | 4 Comments

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4 thoughts on “Demystifying The Tamil Calendar – Thidhis and Festivals

  1. Haripriya

    Very Informative. Thanks!!!

  2. Our Indian system of Calendar is systematic and well thought out covering multiple aspects of each yearly occasion in a mathematical yet precise manner.
    There were some aspects to which I was not clear.
    Your post was Simple and easy to understand. Thank you.
    One request, please post articles on panchangams – why we have different panchangams, how to use them. Thanks again.

  3. rathnamprithviraj

    thanks and its quite info

  4. AK

    Thank you for this…really, i am so lost without internet and such info when it comes to our tradition, etc. I think there is one called Varalakshmi viratham. I am still confused which is celebrated by the iyers..Varalakshmi nombu or Karadiyan.

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