Found a solution.Used Boon's jsonParser to construct Json from string (not Gson's fromJson()) and then casted into List,finally applied sort(),Issue Fixed.
Object jsonObject = fromJson(listloggerdata);
List<?> jsonDepartments = (List<?>) jsonObject;
sort(jsonDepartments,sortBy("Date"));
System.out.println("printing sorted" +jsonDepartments.toString());
the sorted result is
[{"AS2000":["15.0","0","false","false",null,null],"AS1000":["-","-","-","-","-","-"],"Date":"2014-03-02 02:00:00.0"},
{"AS2000":["-","-","-","-","-","-"],"AS1000":["5.1","0","false","false",null,null],"Date":"2014-03-02 08:07:00.0"},
{"AS2000":["-","-","-","-","-","-"],"AS1000":["5.0","0","false","false",null,null],"Date":"2014-03-02 17:58:00.0"},
{"AS2000":["-","-","-","-","-","-"],"AS1000":["5.0","0","false","false",null,null],"Date":"2014-03-14 20:06:00.0"},
{"AS2000":["61.0","0","false","false",null,null],"AS1000":["-","-","-","-","-","-"],"Date":"2014-03-17 19:07:59.0"},
{"AS2000":["27.0","0","true","false","30.0 - 20.0",null],"AS1000":["-","-","-","-","-","-"],"Date":"2014-03-30 06:03:00.0"},
{"AS2000":["-","-","-","-","-","-"],"AS1000":["5.0","0","false","false",null,null],"Date":"2014-03-30 07:00:00.0"},
{"AS2000":["-","-","-","-","-","-"],"AS1000":["5.0","0","false","false",null,null],"Date":"2014-03-30 14:59:00.0"}]
You can even sort based on array index like this
sort(jsonDepartments,sortByDesending("AS2000[0]"));
Hope this might help someone.