How are custom date fields handled? 

Custom date fields are configured as free text fields in Universal Analytics. This means you can only filter custom date fields by selecting static dates from a list, instead of selecting dynamic ranges (Such as last 7 days, 30 days, 90 days).You can filter the list of static dates by month/year, using the search bar above the list. For example, if you only want to display dates from May 2020, enter 05/2020 in the search bar and select All search results (#).