Sometimes, you may need to know how many hours until an event occurs. Typically, you will see this type of calculation in association with a countdown of hours. In order to start the countdown, you need to calculate how many hours there are from the current time until the date of the event. Similar to a countdown, this calculation is also handy for school projects so you know how much time, in hours, you will have to work on a project.

Convert your starting time into a 24hour time. Assume, on 1 p.m. Monday, you want to calculate how many hours it is until 4 p.m. Thursday. So, 1 p.m. translates to 13:00 hours.

Calculate the number of hours it takes to get to the end of your first day. In the example, 24 hours minus 13 hours equals 11 hours.

Count the number of days between the first day and last day. In the example, the days in between are Tuesday and Wednesday. That is two days.

Multiply the number of days in between your first and last day by 24 hours. In the example, 24 hours times two days equals 48 hours.

Determine how many hours are on your last day. In the example, 4 p.m. is 16 hours into Thursday.

Add together the hours on the first day, the hours in between the first and last day and the number of hours on the last day. In the example, 11 hours plus 48 hours plus 16 hours equals 75 hours.
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