Equity SIPs allows investors to systematically purchase certain shares, through periodic payment, either weekly or monthly.
The SIP is executed at 10am on your selected day / date.
If you are placing an SIP order, and the start date/day is the same day, it will get executed the same day if placed before 10AM, else it will get executed on the next selected day / date.
If your selected date for SIP falls on holiday, then your SIP will get executed on the next working day.