According to SEBI, it depends on the time of day! More specifically, the NAV cut-off time for fund redemption.
*Before 3 PM: If your money reaches the Fund House before 3 PM, that particular day's NAV is assigned for unit allocation.
*After 3 PM: If you placed an order after 3 PM, you would get it at the NAV of the next business day.
P.S. NAV or Net Asset Value indicates the current price of one unit within a mutual fund.