We can not say anything about temple subjects.
Because, as we have many sampradayam and have many opinions in doing celebrations
Temples are also following different different agama shastra(?) according to their own decision.
There is no this much of confusion in paste few years back.
Now, due to the development of communication lot of opinions are also spreading through.
So, it is very difficult find out the correct thing.
Now I came to one decision,
Whatever you do according to your circumstance, do not stick on the way of ritual how you are doing
and should stick on and consider the purpose and sincerity, loyalty to the karma.

As per our old syllabus, the time of sankramanam is only important for doing punya kaalaTarpanam and not for Dhanur Pooja Arambam.
Always Dhanur Pooja Arambam and Adi pandikai are to be performed on the first day of the corresponding months.

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As you have told, the 30th pasuram will be recited on 29th day itself.