Other contributors have said "How many days are in a year on Mercurry?" is the same question as "How many days are in a year on Mercury?" If you believe that these are not asking the same thing and should be answered differently, click here
The length of a year (orbit) for Mercury is 88 Earth days, about 1/4 that of Earth. The planet spins 1.5 times during that period, about once every 58.7 Earth days. The combination of these motions...