Here is small presentation on Adhyayana Utsavam.
Parakalan alias Thirumangai Azhwar presented his Thirunedunthandagam on Karthika Pournammi in thr month of Karthigai. to Lord Ranaganatha. Lord Ranganatha was pleased and granted him two boons. Parakalan wanted Thiruvoimozhi to be chanted by Nammazhwr himself as the first boon. Parakalan wanted Lord Ranganatha to bless the conducting of Adhyayana utsavam every year as the second boon.
As regards the first boon Lord Ranganatha ordered Parakalan to go to Alwar Thirnagari and bring Nammalwar. Parakalan goes to Polintha Nindra Piran and requests him to spare Nammazhwar and Polintha Piran refuses initially. To please Polintha Nindra Piran, Parakalan Chants Thirunedunthandagam and gets the permission to take Nammazhwar to Sriranagam. Polinthu Nidra Piran put a condition that Nammazhwar can sing Thirvoimozhi in the night and that too one Paththu( 10*11) pasurams every day. So Thiruvoimozhi chanting was earmarked for 10 daya (Irappathhu). parakalan leaves Alwar Thiru Nagari along with Nammazhwar on Sukla Paksha Prathamai in Margahzi and reaches Srirangam on Dasami, the tenth day. All these ten days on the way the Ghosti that came from Srirangam with parakalan chanted Mudhalaiyiram, Peria thirumozhi etc. That traditon be came Pagal Paththu. Having reached Srirangam on Dasami thithi, Nammazhwars starts chanting Thiruvoimozhi on Ekadasi day with one pathhu everyday for 10 days. On the 10th day of Irappaththu, Nammazhwars gets Moksham but parakalan Prays to Namperumal to return Nammazhwar for the benefit of the world and his request was granted. On the 21st day, Iyarpa is chanted.
The period from karthigai Nakshathiram in Karthigai month to Hastham nakshthiram in Thai month is known as Adhyayana Kalam. Following is a small write up on Adhyayana Utsavam in Tamil. If any factual errors are noticed please bring it to my attention.