The GlobalHistorical and GlobalCorporateActions APIs include the IdentifierAsOfDate input field, which returns the known active date of the provided identifier. If this value is left blank, the value will default to the current date.
For example, Under Armour Class A and Class C were traded under symbols “UA” and “UA.C“ respectively until 12/7/2016. Effective 12/7/2016, the Class C symbol changed from "UA.C" to "UA" (re-use of Class A symbol) and Class A Symbol changed from "UA" to "UAA'. If you input identifier "UA" and IdentifierAsOfDate "12/1/2016" (or any date before the effective date of the change), the API call will resolve to the Class A Share security under the symbol "UA". If you leave IdentifierAsOfDate blank, the API call will default to the current date and resolve to the Class C share security under the symbol "UA".