There is no ideal date for an SIP. Changing your SIP dates would only work if the markets had a clear pattern that played out like clockwork every month. But we all know that market moves are a complete random walk. Splitting your SIPs into weekly installments and trickling them into the fund in smaller doses doesn't have a big pay-off. Your intention in taking the SIP route is to avoid worrying about timing. So pick any date and just stick to it.