Issue #1918994 by Tim Bozeman, mgifford, mpdonadio, vprocessor, sun, xjm,...

Issue #1918994 by Tim Bozeman, mgifford, mpdonadio, vprocessor, sun, xjm, falcon03, nabiyllin, rteijeiro, cwarsaw, yoroy, andymartha, jessebeach, lauriii, jhedstrom, andypost, Bojhan, cilefen, aaronbauman, sugaroverflow: Improve Datetime and Daterange Widget accessibility