Additional time zone shows a one-hour offset on DST start day in Outlook
You use the feature in Microsoft Outlook that displays multiple time zones on the time bar in your Calendar. On the day that the time setting changes for daylight saving time (DST), you might notice that the time difference between your primary and secondary time zones doesn't change.
Additionally, if you use the Full Week view in the Calendar, the whole week shows the incorrect offset between time zones.
The first time zone in your Calendar is (UTC-05:00) Eastern Time (US & Canada), and the second time zone is (UTC-00:00) (Dublin, Edinburgh, Lisbon, London). When the time setting changes for Eastern Time (for example, on March 8, 2020), the time bar in Outlook on that Sunday still shows a seven-hour difference between the two time zones. However, on March 9, 2020, the two time displays show the correct offset between time zones.
This problem occurs because of how Outlook calculates these differences for display in the Outlook user interface.
To work around this problem use the Work Week view. This view starts on a Monday and shows the correct offset between time zones. This workaround should work in most cases. However, if the time zone that you are located in uses a different DST start day than the other time zone uses, the Work Week view might still show the incorrect offset.
Microsoft is researching this problem and will post more information in this article when the information becomes available.