update user guide

Author: christianberkman

user_guide_src/source/libraries/time.rst

@@ -325,6 +325,26 @@ modify the existing Time instance, but will return a new instance.
 
 .. literalinclude:: time/031.php
 
+addCalendarMonths()
+-------------------
+
+subCalendarMonths()
+-------------------
+
+Modifies the current Time by adding or subtracting whole calendar months. Refer to the table below for a 
+comparison between ``addMonths()`` and ``addCalendarMonths()``. These methods can be useful if you require
+no calendar months are skipped in recurring dates.
+
+======= =========== =================== 
+$months addMonths() addCalendarMonths()
+======= =========== ===================
+1       2025-03-03  2025-02-28          
+2       2025-03-31  2025-03-31          
+3       2025-05-01  2025-04-30       
+4       2025-05-31  2025-05-31
+5       2025-07-01  2025-06-30
+6       2025-07-31  2025-07-31
+
 Comparing Two Times
 ===================