Heck! Even they won’t be able to give you a valid answer
Reason being there is absolutely no basis why good performance will repeat in future. If something is not repeatable, then it is worthless.
Choose a day convenient for you. Or when you know you’ll have money in your account on that particular date. That’s all
The key is to increase your SIP amount each year. Stepping up your SIP can help you get rich faster.