The result xs:dateTime has a date component whose value is equal to $arg1 and a time component whose value is equal to $arg2. The result is the empty sequence if either of the parameters is the empty sequence.

The timezone of the result is computed as follows:

If neither argument has a timezone, the result has no timezone.
If exactly one of the arguments has a timezone, or if both arguments have the same timezone, the result has this timezone.
If the two arguments have different timezones, an error is raised:[err:FORG0008]