diff --git a/packages/lib/CalendarService.ts b/packages/lib/CalendarService.ts
index fdd88eed1a..9d1a8316b6 100644
--- a/packages/lib/CalendarService.ts
+++ b/packages/lib/CalendarService.ts
@@ -293,6 +293,7 @@ export default abstract class BaseCalendarService implements Calendar {
     dateTo: string,
     selectedCalendars: IntegrationCalendar[]
   ): Promise<EventBusyDate[]> {
+    const startISOString = new Date(dateFrom).toISOString();
     const objects = (
       await Promise.all(
         selectedCalendars
@@ -306,7 +307,7 @@ export default abstract class BaseCalendarService implements Calendar {
               headers: this.headers,
               expand: true,
               timeRange: {
-                start: new Date(dateFrom).toISOString(),
+                start: startISOString,
                 end: new Date(dateTo).toISOString(),
               },
             })
@@ -359,15 +360,24 @@ export default abstract class BaseCalendarService implements Calendar {
 
         const start = dayjs(dateFrom);
         const end = dayjs(dateTo);
-        const iterator = event.iterator();
-        let current;
+        const startDate = ICAL.Time.fromDateTimeString(startISOString);
+        startDate.hour = event.startDate.hour;
+        startDate.minute = event.startDate.minute;
+        startDate.second = event.startDate.second;
+        const iterator = event.iterator(startDate);
+        let current: ICAL.Time;
         let currentEvent;
-        let currentStart;
+        let currentStart = null;
         let currentError;
 
-        do {
+        while (
+          maxIterations > 0 &&
+          (currentStart === null || currentStart.isAfter(end) === false) &&
+          // this iterator was poorly implemented, normally done is expected to be
+          // returned
+          (current = iterator.next())
+        ) {
           maxIterations -= 1;
-          current = iterator.next();
 
           try {
             // @see https://github.com/mozilla-comm/ical.js/issues/514
@@ -395,7 +405,7 @@ export default abstract class BaseCalendarService implements Calendar {
               end: dayjs(currentEvent.endDate.toJSDate()).toISOString(),
             });
           }
-        } while (maxIterations > 0 && currentStart.isAfter(end) === false);
+        }
         if (maxIterations <= 0) {
           console.warn("could not find any occurrence for recurring event in 365 iterations");
         }
diff --git a/packages/types/ical.d.ts b/packages/types/ical.d.ts
index 2fa435016c..775460f004 100644
--- a/packages/types/ical.d.ts
+++ b/packages/types/ical.d.ts
@@ -121,6 +121,7 @@ declare module "ical.js" {
     public static fromString(str: string): Time;
     public static fromJSDate(aDate: Date | null, useUTC: boolean): Time;
     public static fromData(aData: TimeJsonData): Time;
+    public static fromDateTimeString(aDate: string): Time;
 
     public now(): Time;