CiviCRM Community Forums (archive)

If you have more than a 200-300 memberships I would do this via an export /import.

Use Membership >Find membership and  Export Members via the actions menu.

You must export Membership ID, membership type and membership start date as these are compulsory fields when you do a membership import.  If you have a mix of contact types you should also export that information as you will need to do one import for individuals, one for organisations and one for households.

You would also export membership end date as that is the one you want to change.

Once you have updated the membership end dates, Import Membershipsselecting update existing memberships, using one file for each of the different contact types if applicable.  If you have several thousand memberships you may need to break the file(s) into smaller chunks to import them successfully.