It refers from type of airplane! At least you will be fly 12 hours! Good luck!
To where?
It depends how long you stay in Hong Kong.
Suppose you are to fly from Hong Kong to Toronto, it would take about 15 hours by 747.
16h30
About 12 hours.
14hours
3 hours
15 hours
== == 12 hours
3.8 seconds
15 and a half hours.
About 17 hours.