I filed a bug report with Yealink also and received the following response:
Hi Team,
Hope you are doing great
We are already aware of this.
This is a phone bug.
Two solutions:
1. For single units:
Method 1: Configure the correct time manually:
Step 1: Access the Yealink device’s website
Step 2: Go to setting-> Time & Date
Step 3: Change the Daylight Saving time Automatic -> Enable
Step 4: Change the Fourth week to Last week.
2. For batch modify:
Configure several devices by auto provisioning:
1. Download the correct Default Summer Time configuration file via this link:
https://fileonline.yealink.com/?ShareToken=07590280313B52AABC67E52E0CE58A54BEA279C0
2. Add parameter to the cfg provision file:
auto_dst.url = [http://%3Cserver/]http://<server IP address>/AutoDST.xml
Then upload the configuration file to the server, and get the auto-provisioning URL
3. Access to the device’s website->Setting->Auto provisioning->Fill the Auto provisioning URL with correct information.
4. Press the Auto provision now
Meanwhile, we will fix DST solution in the next firmware version and release in the Yealink (supportyealink.com) website. Please noted.
You can also wait till Sunday and UK time will change.
Then we will release new firmware soon, so that you can manage a time to upgrade all.
Regards,