Compare and return the oldest date

I have a shared workbook comprised of a full report sheet and sheets for individual employees that is being used as a weekly report. Employees enter their weekly totals on their individual sheet, providing:

1. Total pending
2. Total new
3. Total completed
4. Total remaining
5. The date of the oldest work remaining

Each sheet is identical (rows and columns representing each company division and the type of work to be processed), but tailored (by hiding unneeded rows) to the individual processing the work.

The workbook calculates the totals across all of the sheets, and displays the results in the full report sheet; however, I don't know how to compare the dates in the date field across all the individual tabs, and then have only the oldest date displayed in the corresponding cells in the report worksheet. I am currently checking each sheet, then manually entering the dates into the full report sheet. I'm hoping there is an easier way?

If anyone has a (relatively) quick and easy solution, I'd surely appreciate the help. Thanks!