You can set and amend certificate expiry dates in the Certificates tab of an Activity. The guide Award a Certificate will walk you through how to do this.
The new date will only apply to people who are registered on to the activity after the point it was changed.
Anyone who has already completed the activity and been awarded a certificate will be unaffected and their Certificate expiry date will remain the same as when the certificate was awarded.
If needed, you can reset or overwrite a User's expiry date in the Users tab of the Activity.
View the administration area of an Activity. The administration area for content guide will help you if you don't know how to do this.
Click on the Users tab. Tick the User(s) you want to change the certificate expiry date for.
Click on the Actions dropdown menu and choose Set Certificate Expiry Date.
Either recalculate the User's certificate expiry date using the relative date set on the Certificate tab by ticking the option Recalculate expiry date based on completion date.
Alternatively, overwrite the date with a new specific expiry date by selecting the new date from the calendar picker.
Now click Save.