Do you need to complete something at a given time of the day? Do you also know the duration but not the (latest possible) start time? If so, use this free calculator. With a given end time and a duration, you will easily calculate the start time needed to finish the activity in time.
The Calculator for Subtracting Hours and Minutes from an End Time
Enter the time at which your task needs to be completed. Select the duration in hours and minutes using the slider. The calculator will deduct this duration from the end time and show you the start time.
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Ideas for Practical Uses
You might be facing a critical deadline – something needs to be finished by 6 pm, for instance, but there are still other important tasks waiting to be done. Use the end time (6 pm), estimate the duration needed for the completion of the activity and use this calculator to determine the latest possible start time. If it is 2 hours, for instance, your latest start time would be 4 pm. Assuming the estimate is accurate, you could use the time before 4 pm to work on other important things.