Should -et be available?

[Peng Yu]

I don't find a way to test whether two files are at the same time.
Should there be a switch for this comparison given -nt and -ot are
available? Thanks.

       file1 -nt file2
              True if file1 is newer (according to modification date)
than file2, or if file1 exists and file2 does not.
       file1 -ot file2
              True if file1 is older than file2, or if file2 exists
and file1 does not.

-- 
Regards,
Peng