Śrīla Bhakti Sundar Govinda Dev-Goswāmī Mahārāj explains the proper time to observe Śrī Govardhan Pūjā.
In the scripture, it is written,
śrī-kṛṣṇa-dāsa-varyo ’yaṁ śrī-govardhana-bhūdharaḥ
śukla-pratipadi prātaḥ kārtike ‘rchyo ’tra vaiṣṇavaiḥ
(Śrī Hari-bhakti-vilāsa: 16.232)
“During Śukla Pratipad, the first day of the waxing moon, we will worship Girirāj Govardhan.”
In the time of Śrīla Guru Mahārāj, a large disagreement occurred about the style and law for offering worship on Śrī Govardhan Pūjā. Everyone decided that whatever Śrīla Guru Mahārāj will say about it will be most authentic. So, they organised a meeting. I was present at the meeting. It was maybe three to five years after I came, so I was also qualified at that time. So many paṇḍits came as well as many big sannyāsīs: Śrīpād Keśav Mahārāj, Śrīpād Mādhav Mahārāj, and others. A very elaborate discussion occurred, and then Śrīla Guru Mahārāj gave the final decision.
Regarding what will be the time to cook and what will be the time to offer, Śrīla Guru Mahārāj summarised everything in one simple direction. He said to us, “You not do not need to be concerned about so many contradictions. Follow only this: ‘Start cooking during Pratipad tithi and make the offering to Govardhan before the end of Pratipad tithi. This is the law.’”
Then, one only question will come: Mahāprabhu Śrī Chaitanyadev said to Sanātan Goswāmī, “Sarvatra viddhā-tyāga, aviddhā-karaṇa.” This means that if the previous tithi hits the next tithi, that is, if the previous tithi Amāvasyā hits the next tithi Pratipad, then the part of the tithi that has been hit will be rejected, and the other part will be worshipped. I will give you an example. Yesterday, Pratipad started at 9:17 in the morning. Let’s say half past nine o‘clock. So, it started during the day time. That means the sun has already risen and that Pratipad has been hit by the previous tithi. That is called viddhā, and it means that yesterday must be rejected. Pratipad continues today up to 11 o’clock, 11:17. So, we are getting time from six o‘clock [the time of sunrise] to eleven o‘clock [the time Pratipad tithi ends]. This means that we must observe Govardhan Pūjā today because only today will there be no viddhā. So, today our devotees are offering worship. They will finish offering everything before 10:30, and they will finish ārati before 11. In this way, they are following all the rules for Govardhan Pūjā here in this ashram, Śrī Chaitanya Sāraswat Maṭh St. Petersburg. Jay Śrīla Gurudev!
Source
23 October 2006.