Time bubble

A invisiable force of 30 ft is enveloped and resetting time back to 30 seconds. People affected must make a con saving role to regain any hit points they recovered, fail and they don't regain any hit points. Every one restarts from 30 seconds before. If they are resetted out of the time bubble they are not affected by the spell. Anyone who was in the bubble won't know that time is resetted unless they make a wisdom check.