1824347 - Appointments incorrectly displayed on day/week timelines following DST change

Status: RESOLVED DUPLICATE of bug 1797693

(Calendar :: Calendar Frontend, defect)

Description

[andrew]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:109.0) Gecko/20100101 Firefox/111.0

Steps to reproduce:

I am using Thunderbird 102.9.0 (64-bit, build ID 20230310165821) on Win11pro 22H2 22621.1413, and am based in the UK. (User Agent : Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0)

This coming Sunday morning (26/3/23) marks the start of daylight saving time in the UK (i.e. the clocks go forward an hour.) In my Thunderbird calendar, I've just noticed that a repeated calendar entry for 10-12am every Sunday (in the Europe / London timezone) shows correctly for the preceding Sunday and Sundays in the future, but on the day of the time change, it shows on the timeline on the "day" and "week" views at 0900-1100.

This calendar is hosted on a hotmail account, but I note that when I look at it on my phone (Outlook client on Android) this Sunday's appointment is shown at the correct time - I therefore believe that the bug is within Thunderbird.

I have tried taking the appointment out of the repeated entry, firstly by editing it, tn by deleting it and adding it as a new entry and in both cases the appointment was still shown at the wrong time. Experimenting with a test entry showed that all appointments after 2am were shown an hour earlier on the timeline.

Actual results:

All Europe/London timezone appointments on Sunday 26/3/2023 were displayed an hour earlier than they should have been on the day/week view timelines.

Expected results:

These appointment should have been displayed at the correct time.