The ability to make changes in the paycheck depends on the status of the payroll you have run. If the status is not yet processed, you can delete the paychecks, correct the pay date and regenerate the payroll.
Here's how:
Go to the Payroll menu and Employees.
Click the Paycheck list link to open the submitted paycheck.
On the Paycheck list page, click the amount under the Net Pay column to open the paycheck details.
Click the Delete button from the Paycheck page.
Put a check-mark in the I understand that this action cannot be undone checkbox, then hit Delete Paycheck.