I would probably make a hash of hashes, with the first key being the location, the second key being the time, and the value being the person/people working. Ultimately, I would say that it's up to you, your professor, and what lesson you're working on, as this smells very strongly of homework. ;^)

If you are having trouble with it, show us your code and what errors you're getting, and I'm sure we'd be happy to help you learn. . .

- - arden.