What is the start time for new access token generation for the day?

I generated the access token at 4.30am in the morning but the previous day access token was generated.

With this, order placements failed with below message.
order placement failed for BANKNIFTY21DEC34500CE at time 2021-12-27 09:36:00.170339 because Incorrect `api_key` or `access_token`.

So, my questions are
1. What is the earliest time in the day I can generate access token and use for the day?
2. If I invalidate access_token at 4am in morning and generate fresh access_token, can that be used for the rest of the day.

Asking as there might be days where I will not have my network access after 4.30am. So, looking for a workaround in those days.