Booking sytem sends wrong ics file to those using apple calendar

Huw Pearson 0 Reputation points
2026-09-09T15:45:58.4633333+00:00

I have check every setting and cant figure it out. Unfortunately this is confusing for my clients as booking = 1 time and calendar inputs 1 hour later.

Chat GPT answer:

We have identified a timezone issue with Microsoft Bookings calendar invitations.

Microsoft Bookings generates an ICS calendar attachment using the timezone "GMT Standard Time". Outlook displays the booking correctly, but Apple Calendar displays the appointment one hour later during British Summer Time (BST).

The generated ICS file contains a VTIMEZONE definition for "GMT Standard Time", but the STANDARD and DAYLIGHT components do not contain RRULE definitions for the UK daylight-saving transitions.

For example, the generated file contains:

[Moderator note: Personally Identifiable Information removed]

Outlook displays this correctly at 19:00, but Apple Calendar interprets it as 20:00.

Please investigate the Microsoft Bookings ICS generation/timezone definition and confirm whether this is a known issue or whether there is a Microsoft-side fix available.

We need the ICS generated by Bookings to work correctly for Apple Calendar users without requiring customers to manually change their calendar settings.

Outlook | Web | Outlook on the web for business | Calendar
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  1. Ivory 1,155 Reputation points Independent Advisor
    2026-09-09T16:13:19.77+00:00

    Hi Huw,

    To investigate the issue where the appointments in Microsoft Bookings and Apple Calendar appear one hour later than scheduled, please try following these troubleshooting steps: 

    Uncheck “Always show time slots in business time zone” 

    • Go to Microsoft Bookings > Booking Page.
    • Uncheck the box for: “Always show time slots in business time zone”
      User's image

    Check iCloud calendar time zone support 

    1. On iCloud.com: 
      • Go to Calendar > Preferences > Advanced.
      • Make sure Time Zone Support is enabled and set to the correct zone (e.g., Amsterdam).
    2. On iPhone/iPad: 
      • Go to Settings > Calendar > Time Zone Override.
      • Try toggling this off or on, depending on your current setting, and test again.

    However, this is a potentially complex issue from multiple angles that requires back-end verification from the Microsoft Support team.  

    Given the nature of the problem, the most effective next step is reaching out to your IT admin and ask them to use their admin credentials to submit a support request through the Microsoft 365 Admin Center on your behalf.

     

    Microsoft also provides customer service phone numbers based on your region. Your IT admin can find the appropriate contact number here: Customer service phone numbers - Microsoft Support 

    This route ensures that a Microsoft support engineer can initiate a remote session to investigate backend configurations, run advanced diagnostic tools, and, if necessary, they can request to escalate the case to specialized teams with access to internal systems and logs. These backend resources are essential for resolving issues that go beyond what’s visible in the user interface.

    In case you do not know who is your IT admin, kindly refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support 

    I hope this helps you resolve the issue quickly. I’m glad to assist and truly hope the information provided has been useful. Please feel free to reach out anytime if you need further assistance.  

    Thank you for your kindness and contributions to the forum. 

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