Issue #2826404 by mpdonadio, Jo Fitzgerald, jhedstrom, larowlan: Create...
Issue #2826404 by mpdonadio, Jo Fitzgerald, jhedstrom, larowlan: Create DateTimeItemInterface and deprecate global constants in datetime.module
Issue #2826404 by mpdonadio, Jo Fitzgerald, jhedstrom, larowlan: Create DateTimeItemInterface and deprecate global constants in datetime.module