What is Sunday?
The countdown above runs to the midnight where Saturday ends and Sunday begins where you are. Sunday is the day the week is least able to agree about: the United States, Canada and Japan treat it as the first day, while ISO 8601 and most of Europe put it last, and across much of the Middle East and parts of South Asia it is a working day because the weekend fell on the Friday. None of that changes the midnight, only what the day is called once it arrives.
Sunday is the quietest day of the week for services almost everywhere, which is usually why anyone is counting towards it. Shops in Germany, Austria and Norway are closed by law apart from narrow exceptions for bakeries, petrol stations and station concourses. Railways in Britain and much of Europe use the day for engineering work, so a Sunday journey is worth checking against a timetable rather than assumed from the weekday one. Deliveries fall to a handful of carriers. The practical effect is that Sunday suits anything that needs uninterrupted hours and suits nothing that needs another organisation to answer.
In Israel, Egypt and much of the Gulf this is the first working day of the week, so a Sunday message from Tel Aviv or Cairo reaches a European desk that is closed, and the same happens in reverse every Friday. Britain keeps a roast lunch and a separate set of Sunday newspapers with their own staff and deadlines. Argentina gives the day to a long family asado. American professional football concentrates almost its whole season into Sunday afternoons and evenings. The common thread is that the day was set aside for worship first and everything else arranged itself around the gap.
The next one falls on the next Sunday, and this page counts down to the midnight that starts it in whatever time zone your browser reports.