This could be used to check whether a package is possibly reproducible. 
Then it could make sense to add a reasonable SOURCE_DATE_EPOCH value to 
the cygport file.

Example:

$ export SOURCE_DATE_EPOCH=$(date +%s)

$ cygport project.cygport all repro-check
...
*** Info: Build reproducibility test succeeded

$ TZ=UTC cygport project.cygport repro-check
...
*** Info: Build reproducibility test succeeded

$ unset SOURCE_DATE_EPOCH

$ cygport project.cygport repro-check
...
*** ERROR: Build reproducibility test failed

-- 
Regards,
Christian