About 12 hours
It depends. If you fly non-stop from London it will take about 14 hours. Stopping over will obviously take longer. Flying non-stop from further north in the UK will take longer at about 15 hours.
Heathrow to Shanghai 10.5hours
it will take more than 2 hours to travel
it will take about 9 hours
About 5 hours depending on which part of London.
About 7-8 hours to travel London to Muscat.
Around 4 Hours
About 3 hours
7 Hours
About four hours.
About five hours by road.
I did this trip last month and will again in July, if you stop over in London (there are no direct flights from dublin to shanghai. Most of the time you will stop here but can also choose other euro stops.) it is aprox 12 hours from London to shanghai. It took me just a shade under. less than an hour to London means 13 hours. Obviously you will need to add the layover time in lonndon as well. This will vary from flight to flight. I flew Virgin and it was 3 hour 50 min stop on the way to shanghai. Just 2 on the return. That is 17 hours give or take five to ten minutes to get from Dublin to Shanghai. The shortest possible time would be 14 and a half to 15 hours (With a one hour to 90 minute stopover in England. Due to the check in one hour before flight all flights have a 90 minute minimum stopover.) So to answer your question expect the actual in plane part to take 13 hours (1 to London and 12 London to Shanghai.)