All times, by default, refer to BST (British Summer Time). The BST sign is visible in all areas of the programme. However, each participant can set its own time zone to a number of possibilities. To do this, please go to your setting cog wheel - the symbol between the mail and star symbols - which appears when you are logged in, scroll to local setting and choose the city in the country you are based.
Please note that the times displayed when you enter the ZOOM waiting rooms are by default in CEST (+1 on BST)