I would say not much different from looking up whether they are in the +0530 or +0630 part of India. I guess the perception of convenience also depends on what you are used to seeing.
That information won’t be lost, though. It just would be expressed differently. They are no longer in a +8 hour time zone, which given your own location in a +1 hour zone would lead to a most likely open time of 8 - 8 + 1 = 1 til 17 - 8 + 1 = 10 your time, but in an area where opening hours are most likely between 0100 and 1000.
There is still a lookup, but no longer a lookup of time difference of the area, but a lookup of usual business hours in the area.