The clocks and scheduling on the AppCheck scanner front end (web portal) are set to civil time in the United Kingdom/London local time
This is usually Greenwich Mean Time (GMT), which tracks Coordinated Universal Time (UTC+00:00). During the British summer months (typically around 31st March to 27th October), London local time switches to British Summer Time (BST). BST is advanced one hour forward of GMT (in effect, changing the time zone from UTC+00:00 to UTC+01:00).
Within the back end, all systems in AppCheck operate on UTC time so the start and stop times for scans are stamped with those.
When scheduling scans, the times entered are always in London local time (GMT/BST depending on time of year).