Returns true if the two supplied xs:dateTime values refer to the same
            instant in time.
xs:dateTime values. Also
         used in the definition of the "ne", "le" and "ge" operators.op:dateTime-equal( $arg1 as xs:dateTime,$arg2 as xs:dateTimexs:booleanIf either $arg1 or $arg2 has no timezone component, the
            effective value of the argument is obtained by substituting the implicit timezone from
            the dynamic evaluation context.
The function then returns true if and only if the effective value of
               $arg1 is equal to the effective value of $arg2 according to
            the algorithm defined in section 3.2.7.4 of 
				Order relation on dateTime for xs:dateTime values with
            timezones. Otherwise the function returns false.
Assume that the dynamic context provides an implicit timezone value of
                  -05:00
				
The expression op:dateTime-equal(xs:dateTime("2002-04-02T12:00:00-01:00"),
                  xs:dateTime("2002-04-02T17:00:00+04:00")) returns true().
The expression op:dateTime-equal(xs:dateTime("2002-04-02T12:00:00"),
                  xs:dateTime("2002-04-02T23:00:00+06:00")) returns true().
The expression op:dateTime-equal(xs:dateTime("2002-04-02T12:00:00"),
                  xs:dateTime("2002-04-02T17:00:00")) returns false().
The expression op:dateTime-equal(xs:dateTime("2002-04-02T12:00:00"),
                  xs:dateTime("2002-04-02T12:00:00")) returns true().
The expression op:dateTime-equal(xs:dateTime("2002-04-02T23:00:00-04:00"),
                  xs:dateTime("2002-04-03T02:00:00-01:00")) returns true().
The expression op:dateTime-equal(xs:dateTime("1999-12-31T24:00:00"),
                  xs:dateTime("2000-01-01T00:00:00")) returns true().
The expression op:dateTime-equal(xs:dateTime("2005-04-04T24:00:00"),
                  xs:dateTime("2005-04-04T00:00:00")) returns false().