Hi Joshua,
The custom script is scheduled on a server where ArcGIS Server 10.5 is running. The test I did was done on Desktop 10.5 using featureclass\table on a 10.5 SDE and 2012 SQL server instance. Python install version we are using is 2.7.12. The code below is simple one to test,
egdb = r'dataconnection\somedb.sde'
egdb_conn = arcpy.ArcSDESQLExecute(egdb)
sql = '''SELECT DATEFIELD FROM SOMEDATA'''
egdb_return = egdb.execute(sql)
the tuple returned by running this piece of code using the 10.5 setup (on server and desktop) will yield blank strings while when using just a 10.3 desktop install on a separate machine it extracts the datetime values correctly.