SotBE S18: use simpler and more robust check for afternoon time

This one will also happen in the afternoon if the scenario start time
of day gets changed.

data/campaigns/Son_Of_The_Black_Eye/scenarios/18_Northern_Alliance.cfg

@@ -259,8 +259,6 @@
 
         {GENERIC_UNIT 6 (Royal Guard) 45 22}
         {GENERIC_UNIT 6 (Royal Guard) 47 21}
-
-        {VARIABLE afternoontime 3}
     [/event]
 
     [event]
@@ -611,23 +609,16 @@
         name=new turn
         first_time_only=no
 
-        [set_variable]
-            name=afternoontime
-            add=1
-        [/set_variable]
+        [store_time_of_day]
+        [/store_time_of_day]
 
         [if]
             [variable]
-                name=afternoontime
-                numerical_equals=6
+                name=time_of_day.id
+                equals=afternoon
             [/variable]
 
             [then]
-                [set_variable]
-                    name=afternoontime
-                    sub=6
-                [/set_variable]
-
                 [gold]
                     amount=500
                     side=4
@@ -642,6 +633,8 @@
                 {GENERIC_UNIT 4 Horseman 22 37}
             [/then]
         [/if]
+
+        {CLEAR_VARIABLE time_of_day}
     [/event]
 
     [event]