Adding and subtracting
Pick a start time, choose Add or Subtract, and fill in any of hours, minutes and seconds. 21:15 plus 5 hours 50 minutes is 3:05 AM the next day. Values past 59 are fine: 90 minutes is read as 1 hour 30.
Past midnight
When the answer runs past midnight, the line under it says so: the next day, the day before, or how many days later. Adding 100 hours to 09:00 lands on 1:00 PM, 4 days later.
Questions
What time will it be in 8 hours?
Set the start to the time now and add 8 hours. The page opens on 09:00 plus 8 hours, which is 5:00 PM.
Can it count the hours between two times?
That is the Hours Calculator. To add up several durations, use the Hours and Minutes Calculator.