Buzzb, the sum of 3d and 15d equals the date of the setting of the puzzle. I was positing an assumption that the date would be 1967 or later.
However, the reference to a Time Travel department does rather complicate things.
Unless I have 22ac wrong, I think there are only 3 options for 14d. One of those has a prime that I think is too large for any of the entries where it might go.