You can use the XPath constraint:
[day-from-dateTime(JoiningDate) = day-from-dateTime('[%CurrentDateTime%]')]
[month-from-dateTime(JoiningDate) = month-from-dateTime('[%CurrentDateTime%]')]
More info on XPath dateTime fuctions: https://docs.mendix.com/refguide/xpath-constraint-functions/
(Be aware that the day-of-year-from-date function does not work for days after Feb 28th when comparing leap years with non-leap years)