When you activate Microsoft Office, the date from your computer's clock is recorded as the subscription start date. This date information is checked periodically to ensure that your subscription hasn't expired, and to schedule renewal reminders. This dialog appears when Microsoft Office detects a discrepancy between the expected date and the date reported by your system clock.
To manually correct the clock date (and time zone, if necessary), click the Set Date button to launch the Adjust Date/Time control panel application and make the change.
If you have an Internet connection and want to validate that your clock has the correct setting, click the Verify Date button. This will connect you to a Microsoft server where your computer's clock setting will be verified, and the problem corrected if it is not due to an incorrect clock setting on your computer. If your computer clock is set incorrectly, then you should manually correct the clock date and time zone by clicking the Set Date button.
If you don't correct the clock settings, Microsoft Office will go into Reduced Functionality Mode. In that mode you will not be able to save modifications to documents, or create a new document, and additional functionality may be reduced.