Quicken reconciliation not matching balanced bank statement

I manually balance the checkbook with the bank statement then update the Quicken register with any new transactions and do the Quicken reconciliation. The manual balancing and Quicken reconciliation normally match and the final balance in the Quicken register matches the ending balance in the checkbook, as it did when I balanced the 1/15 and 2/15 bank statements. The 3/15 statement balanced with the checkbook, but the balance in the Quicken register and reconciliation is $1500.00 higher than the checkbook balance. There were only a few transactions since the previous statement none of which was $1500.00. There were 2 $750.00 checks with February dates, both of which cleared on the 2/15 statement and Quicken register. One of those checks was written and originally entered in the Quicken register in January, but I edited the date in the register and my checkbook to the February date that I actually gave the check to the payee. I changed no other field in the register entry. Is there any way the cleared balance in the reconciliation and ending balance in the register could have been affected by the changing of the date? Is there any way to view or redo a previous month's reconciliation?