Extended date range


Question: I’m making an archival collection with materials that have different period qualifications.
Some can be designated to a very precise date eg 8-15-2015, others have a more extended period like 8-15-2015 tot 10-20-2015. What we we a good way to enter this date period so that it’s intelligible and workable for the system without having to add all the different dates that apply manually?