Yaagam of any kind shall begin only in the 'Velutha Paksham' (the fortnight between new moon and full moon) of Vasantham season (spring, April-May). It shall also fall on one of the five auspicious stars - Karthika, Rohini, Punartham, Makam or Uthram-, and the selected star shall be otherwise astrologically auspicious too for performing any ritual. The importance of the auspicious day actually applies to the ritual called 'Aahavaneeyam Viharikkal', performed at the dawn as a part of the one-and-a-half day Aadhaanam. Since the preparatory rituals before 'Aahavaneeyam Viharikkal' take one full day, the start of Aadhaanam shall be the day before the selected day.

Let us look at how the starting date of Aadhaanam and the subsequent Somayaagam-2003 (Agnishtomam) in the Thrissur Brahmaswam Madham, was arrived at. The first auspicious star, Karthika of Velutha Paksham in Vasantham was on 6th April, which was otherwise an astrologically in-auspicious day and hence discarded. The next good star, Rohini was found to be astrologically auspicious, and fell on 7th April and hence the dawn of that day was selected for performing 'Aahavaneeyam Viharikkal' of Aadhaanam. Thus the previous day, 6th April was chosen to begin Aadhaanam, and thereafter, at the noon of 7th April, the Somayaagam was commenced.

If the Somayaagam immediately precedes Aadhaanam, there is no need to look for an auspicious day for Somayaagam.

If, however, Aadhaanam has been performed not immediately preceding yaagam, but earlier, then the auspicious day is reckoned so that the end of Suthyam ( the final day of yaagam) falls on Prathipadam (first day of the lunar fortnight, Paksham). As a second choice, instead of Prathipadam, the Vaavu (the last day of the lunar fortnight) is also acceptable.

Separate from yaagam and following it, the yajamaanan has to perform Darsapoornamaasyeshti on every Prathipadam (fortnightly) thereafter until the yajamaanan or his wife dies.

If the yaagam is disrupted owing to the wife having her periods, the yaagam itself has to be broken and continued immediately after the periods. In that case, the first Darsapoornamaasyeshti has to be postponed to the next Prathipadam.