如何根据用户未来选择的时间获取总小时数

Is possible to find total number of hours when a user has selected a future time for example, if the current time is 12:00PM and user select to finish a task in the next 2 hours 2:00PM as the target time, how can I represent those 2 hours like this " Time to complete next task 2Hours" Is possible to find total number of hours when