From Longman Dictionary of Contemporary Englishtime capsuleˈtime ˌcapsule noun [countable] SHa container that is filled with objects from a particular time, so that people in the future will know what life was like then
Examples from the Corpus
time capsule• A time capsule containing personal messages of hope for the next generation will be buried during closing ceremonies.• Music greeted us when we walked through the old swinging doors, original doors that led to the Delaney time capsule.• The new exhibition areas will allow the Trust to display even more of the contents of this remarkable time capsule.• Your donations should be sent to Oxford Preservation Trust, and you will be sent the time capsule. 