The only way to do this that I know is to disable auto-renewal temporarily and then manually buy the next membership for each on the same day and then reenable auto-renewal.
From then on all three accounts will auto-renew on the same day.
But this may mean a few days without service for two of the accounts while you wait to sync them up.
I don't think that you can change the auto-renewal date any other way.
But maybe contact 48 support and ask them if there's any other way.
See the links in my signature below.
