Flights are available daily starting in the middle of January through early April, which would be a good time for an escape from the Michigan and Minnesota winters. A Saturday night stay is required, and on some itineraries, there might be a long layover or overnight required, those are mostly for the Minneapolis departures.
As an example, searching on Orbitz, I found tickets departing DTW on Tuesday, January 22 and returning from HKG on Monday, February 11, 2019. It is best to book through a third-party site, like Priceline or Orbitz as their prices are about $25 less than what the Air Canada site is offering. But if you feel more comfortable booking directly with the airline, it will cost $461 for most dates.
This is the last day of Air Canada's Fall Sale, so if you are interested in these fares, I recommend you book them ASAP as they probably won't be around tomorrow at this price. If you are on the fence, the third-party sites I listed above will allow for free cancelations within 24-hours, so you can purchase now and cancel tomorrow if you change your mind.
If you need a place to stay in Hong Kong, we've got you covered with a long list of options provided by Hotelwatchdog.