Hi,
You are facing this problem because of report widget contains the date column with Time-stamp.
You can achieve it by following ways:
1. While saving/pushing the records into the collection you can use only MM/dd/yyyy. So that it will export the file as per proper format(required).
2. If your requirement is- you wanted to show the records in the report widget with Time-stamp then you have to use the JavaScript on button(with action as Execute Script) which will execute after clicking on it.Inside the JS you have to use the code which will fetch all the values (with date format as per your requirement) from the collection and create.export the file.
3. You can also modify your exported file's column as per required date format cell inside the file (if any) provided by the vendor.