Thanks for posting here in the Community, eprman. You've come to the right place for help with your QuickBooks and Square connection.

Is it possible the transactions in question are partial payments from your customer(s)? Square sends payment details to QuickBooks when the final payment has been made to close the order. Several partial payments may be the cause of the different dates you're seeing. 

I've got an article for you that covers the ins and outs of connecting Square to QuickBooks. You can check it out here: Connect your Square account to QuickBooks Online

Please don't hesitate to reach back out if you need help with the Square transactions or anything else. Take care!