diff --git a/src/recurrence.cpp b/src/recurrence.cpp
--- a/src/recurrence.cpp
+++ b/src/recurrence.cpp
@@ -1049,14 +1049,7 @@
         }
     }
     sortAndRemoveDuplicates(extimes);
-
-    int st = 0;
-    for (i = 0, end = extimes.count();  i < end;  ++i) {
-        int j = times.removeSorted(extimes[i], st);
-        if (j >= 0) {
-            st = j;
-        }
-    }
+    inplaceSetDifference(times, extimes);
     return times;
 }
 
@@ -1116,15 +1109,7 @@
     }
     extimes += d->mExDateTimes;
     sortAndRemoveDuplicates(extimes);
-
-    int st = 0;
-    for (i = 0, count = extimes.count();  i < count;  ++i) {
-        int j = times.removeSorted(extimes[i], st);
-        if (j >= 0) {
-            st = j;
-        }
-    }
-
+    inplaceSetDifference(times, extimes);
     return times;
 }
 
diff --git a/src/recurrencehelper_p.h b/src/recurrencehelper_p.h
--- a/src/recurrencehelper_p.h
+++ b/src/recurrencehelper_p.h
@@ -33,6 +33,18 @@
     container.erase(std::unique(container.begin(), container.end()));
 }
 
+template <typename T>
+inline void inplaceSetDifference(T &set1, const T &set2)
+{
+    auto beginIt = set1.begin();
+    for (const auto &elem : set2) {
+        const auto it = std::lower_bound(beginIt, set1.end(), elem);
+        if (it != set1.end() && *it == elem) {
+            beginIt = set1.erase(it);
+        }
+    }
+}
+
 }
 
 #endif