In most cases, pilots are paid hourly so that they are directly covered for the specific amount of flight hours that they complete. However, as a lot of flights are pre-scheduled most pilots will know how many hours they will be expected to work per month, and they will be able to work out their annual salary from that. However, it is important to remember that pilots are only paid for flight hours, so this does not involve time spent in the cockpit or pre-flight planning. Essentially, pilots are not paid for anything other than the time that they are in the air.
So in a lot of cases, pilots are paid hourly. These hours only include flight hours, and for this reason, they will usually be paid for about 85 hours a month. There is a limit to the amount of hours that a pilot can fly, but as long as a pilot is under their hours then they can pick up additional flights which will impact the amount that they are paid. But generally speaking, a pilot will expect to be paid hourly for approximately 85 hours per month by their employer.