NAV is updated every day after market hours from Monday to Friday and released by the AMCs by the end of the day, which is by 9 PM. So, Mutual funds NAVs are based on the value of the previous date.
For example, on 3rd May, the NAV value that you see will be on 2nd May. And 3rd May’s NAV will be updated after market hours on 3rd May. So during the day, on 3rd May, you will see the NAV of 2nd May.
It is not updated on Saturday and Sunday since they are holidays.
Some special Mutual Funds’ (FoF) NAVs are updated once a week.