Reverse Time Calculator
Calculate the start time or end time given a duration and one of the times. Useful for planning events, travel, or deadlines.
Published by:
isCalculator Editorial Team
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How to use this tool?
This calculator computes any missing value (Start Time, End Time, or Duration) given the other two. It automatically handles time crossing midnight.
- Select what to calculate from the dropdown: Start Time, End Time, or Duration.
- Fill the two known fields:
- If calculating Start Time: enter End Time and Duration (hours/minutes).
- If calculating End Time: enter Start Time and Duration.
- If calculating Duration: enter both Start and End times.
- Click Calculate to see the result and the formula used.
- Use Clear to reset all fields to default values.
Note: Times use 24-hour format (e.g., 08:00 for 8 AM, 17:00 for 5 PM). Duration accepts hours (any positive number) and minutes (0–59). The calculator automatically wraps times past midnight.
Previous Results
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Frequently Asked Questions
It calculates the missing time component (start, end, or duration) when you provide the other two. For example, if you know the end time and duration, it finds the start time.
Select what you want to calculate from the dropdown (Start Time, End Time, or Duration). Fill in the known fields and click Calculate. The result will appear below.
Yes, the calculator accounts for times that cross midnight by adding 24 hours if the result is negative.