Period End Date is the date that is entered when you Enter Time or Enter Checks. The Check Date is the date you enter when you print checks. Companies may use different dates for these dates when performing these tasks - or - they may use the same date for each task. When it comes to the 941, it's the Check Date. This is because the W-2's should balance back to the 941s and the W-2's are based on the Check Date.