Information about temples of India never ceases to amaze me.The intimacy with which God is related to by people is unique to Santana Dharma.
Though the Vedas,one of the sources for Sanatana Dharma,enunciates the Concept of Reality as The One Beyond Attributes , A Principle that is beyond Mind , the worship, the emotional connect of people to God in Hinduism is beyond one’s comprehension, if one is not a practising Hindu. Realising Brahman, The Reality, as A Principle by various practices is Nirguna Aradhana, worshipping It one beyond Attributes,though the term worship is not correct in place of Aradhana.As Dwelling upon A principle that is beyond Attributes is ,it appears to human Mind,a tough proposition, Hinduism suggests the practice of relating to Personal God/ Goddess. This method is called Sabina Aradhana,that is relating to a Personal God,Iswara, with Name, Form and Attributes in Perfection/ In Full measure.The Name and form might be that of reator,sustainer,destroyer,Father,Mother,Lover,Spouse, …That depends on one’s likes . If you can easily connect to Mother, the Concept of God is Mother and all the qualities we find and we expect to find in Mother to our Happiness, those qualities are ascribed to God, in this case,Goddess.The same process applies to other relations as well.One connects to this form emotionally without any mental blocks and rationalisation as reason belongs to mind and not to 💓.One relates to this concept of God easily and strongly. This is the power of Saguna Aradhana. Hindu texts state that this mode of relating to the Reality, is akin to one doing pre Kindergarten before obtaining PhD. One can not get PhD, without kindergarten, though it might look unnecessary after obtaining PhD.Hindus sastras declare that when one relates to Reality through Sabina Archana thus, one would migrate to Nirguna Aradhana, without one realising it. Thus one one Experiences Reality. That is what Matters.
So much the relationship between Man and God is, God is treated with all the attributes of Man and all emotions one undergoes, one’s elations, pains are ascribed to Him and they are celebrated in Temples. This includes The early morning waking up, Brushing up of teeth,taking bath…Not only this, God marries and it is celebrated. Though God is Eternal and Unborn, His Birthday is celebrated.
Thus one finds Festivals in In Indian temples,celebrating these events,called Utsavams.The Utsavams are performed for the idol specially made . This is is different from the Deity in the Sanctum. The Deity in the Sanctum is never moved and the Deity is called Moolavar.Every temple has its festivals.And these Festivals are many, spread over the twelve months of a Year.

The Sri Rangam Temple, the second most Holy Shrine of Sri Vaishnavas, the first being Vaikuntam located celestially,is the second largest temple in the world, next to Angkovat, Cambodia. In terms of being the largest Functioning Temple Srirangam Takes the pride of place.
I shall be writing in detail about Srirangam Temple.
Srirangam celebrates Three Hundred Twenty two Festivals in one Year. I will post about some important festivals of Srirangam in the succeeding post.
Find below details regarding the festival details in Srinrangam, in PDF format. You may download it. This relates year 2019 -2020.However, you can refer it as it contains detailed information on Srirangam Temple, including Individual deities in the temple.This is in Tamil. Am looking for English version. Readers may contribute.
https://ramanan50.files.wordpress.com/2021/04/wp-1618554746968.pdfhttps://ramanan50.files.wordpress.com/2021/04/wp-1618554746968.pdf
Source. Good source for Information on Srirangam.