Can dateTimes be used as keys in a dictionary? I need to associate key hours to temperatures values and also need to be able to span days. Or would you just calculate a key using (dateTime.dayofyear * 24 + dateTime.hours in today) to associate an hour key in the year?
A DateTime would not work as a key in this situation. Use your calculated value instead.
Also make sure that your calculated value will be unique otherwise you will run the risk of writing over an existing key / value that has the same key by accident.