Do you mean import from Excel (.xlsx)? If so, FM should import internal data from the file, not depend on presentation format in the Excel file.
I export the data from one FileMaker solution as an .xmls file and import it into a different solution. When exported and reviewed in Excel, all times are correct. When I import them into the second solution, times after 12:00 noon come in as ?. I have to re-enter the times.
I tried with FM14 and .xlsx (there is not .xmls) but couldn't reproduce.
Which version do you use?
Do your second solution use 12-hours format?