All-day events in Outlook are shifted by one day in Hubspot

[Clubman]

We are currently experiencing (or have never experienced) issues with our appointment scheduling via Hubspot.

Issue description:

Full day events (even multi-day events like vacations or absences) are not showing up correctly in Hubspot meeting scheduler. They are always shifted by one day. Sometimes a one-day event is shown as 2 days long and shifted by one day.

We have already had to reschedule several customer appointments because of double bookings. Currently, we always check the Outlook calendar and then book the appointment there. This means that Hubspot's meeting planner tool is not an added value.

Our system:

- Hubspot Professional Customer Platform

- Microsoft 365/Teams

- We use both Outlook (new) and the website outlook.office.com

What we have already checked.

- All calendars are linked correctly

- Plugin is up to date

- Client time zone set correctly

- Microsoft tenant time zone set correctly

- Time zone determination in Hubspot (client, but also turned off for testing, no effect)

Error can be reproduced as follows:

1. creation of an all-day event in Outlook (Busy)
   
2. the event created here on 23.04 in outlook is displayed in Hubspot on 24.04 (postponed by one day)
   

1. The timestamp of the display is in Unix time (HTML source)
   
   Which translates to 24.04 (which is wrong)
   

But this works as intended:

1. If you create the event for this day from 00:00-23:30 (not an all-day event), it will be displayed correctly  
   
   
   
   
2. a two-day event is also displayed correctly
   

This does not work:

1. as soon as you check the “All day” box again, it no longer works and the event is shown postponed by one day. 
   

   The timeline also looks a bit off (this is not the case at the top, but it is already summer time in April)

My guess:

- Either this is a display error on the Hubspot site with the calendar

- The plugin determines the wrong date for all-day events

- Hubspot determines the wrong date from Outlook

Additionally:

All-day events are not displayed grayed out, but only as a small entry at the top. Appointments with 00:00-23:59 are displayed correctly in the day view as “busy”. For the sake of clarity, all-day appointments should also be displayed as busy (grayed out) in the hour selection, not only on the top.

[PamCotton · Accepted solution]

Hey @Clubman, thank you for posting in our Community!

And thanks for sharing the details. The issue could be related to time zone settings, how HubSpot handles all-day events, or a syncing problem with the Outlook plugin. 

Double-check that both Outlook and HubSpot have the same time zone settings, including daylight saving time. 

If possible, try setting the start and end times for all-day events as 00:00-23:59 instead of using the "All Day" checkbox. If the issue persists, consider reinstalling or clearing the cache for the Outlook plugin.

Let us know how this works.

Kindly,

Pam

[Clubman]

Dear Pam,

thank you for your reply and suggestions.

We've thoroughly reviewed all time zone settings across our Microsoft tenant, individual devices, and within HubSpot itself. Everything is consistently configured, including daylight saving time. Therefore, we are confident that the issue is not time zone-related.

The problem appears to lie specifically in how the Outlook plugin handles all-day events during synchronization. All-day events created in Outlook (using the "All Day" checkbox) are consistently shifted by exactly 24 hours when displayed in HubSpot. As a result, employees are mistakenly shown as available, which has already led to incorrect bookings. We have monitored this behaviour the last weeks.

As a workaround, we avoid using the "All Day" option and instead define all-day absences and holidays with explicit times from 00:00 to 23:59. This ensures the correct date is displayed in HubSpot and the user is shown as not available. However, this leads to a second issue:

When events are defined with a time range of 00:00–23:59 for more than one day, they appear only as thin banners at the top of the HubSpot calendar and do not block availability in the hourly view. This applies only to multi-day events (not "All day" but 00:00-23:59). Consequently, users are incorrectly marked as available for the entire day, despite being on leave.

In summary, we believe the issue stems from how the HubSpot Outlook plugin interprets and syncs the start time and date of all-day events. Moreover, we would highly appreciate an enhancement where full-day absences—whether defined by time or as true all-day events—are shown as fully unavailable across the calendar, in line with how Outlook treats them.

We appreciate your attention to this matter and would be happy to support further investigation.

Kind regards,
Chris