Westminster Abbey:

The Westminster Abbey Museum is located in the 11th-century vaulted undercroft beneath the former monks' dormitory in Westminster Abbey. This is one of the oldest areas of the abbey, dating back almost to the foundation of the church by Edward the Confessor in 1065. This space has been used as a museum since 1908.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". The vaulted undercroft beneath the monks' dormitory hasn't been a museum since when?
unanswerable