Add NEWS entry

Author: derickr

NEWS

@@ -15,6 +15,10 @@ PHP                                                                        NEWS
   . Fixed bug GH-15501 (Windows HAVE_<header>_H macros defined to 1 or
     undefined). (Peter Kokot)
 
+- Date:
+  . Fixed bug GH-13773 (DatePeriod not taking into account microseconds for end
+    date). (Mark Bennewitz, Derick)
+
 - MySQLnd:
   . Fixed bug GH-15432 (Heap corruption when querying a vector). (cmb,
     Kamil Tekiela)