Cross midnight explicitly
An earlier end time is not silently treated as the next day.
051 · DATE & TIME
Time Calculator
Add or subtract time, calculate the difference between two times, and convert between 12-hour and 24-hour formats.
LOCALCALCULATE IN YOUR BROWSER
LOCALTimes and calculation values stay in this browser and are not sent to or stored on a server.
Duration
RESULT
12:05
HOW TO USE
How to use
- 01
Choose Add/Subtract Time, Time Difference, or 12/24-hour Conversion.
- 02
Enter the base time or start and end times.
- 03
Enable Cross midnight explicitly when the interval passes midnight.
- 04
Review the resulting clock time or elapsed duration.
- 05
Copy the result or reset the calculator when needed.
TIME CALCULATION GUIDE
Midnight and 12 AM/PM rules for time calculations
Clock time and duration are separated, while calculations use normalized total seconds.00:00 / 12:00
12 AM maps to midnight; 12 PM maps to noon.
Automatic carry
Minute and second boundaries are normalized from total seconds.
IMPORTANT NOTES
Important notes
- When the end time is earlier, the calculator does not silently assume the next day.
- 12 AM is midnight (00:00), while 12 PM is noon (12:00).
- Duration input is designed for up to 999 hours 59 minutes 59 seconds.
- Time zones belong to TOOL052, Unix timestamps to TOOL053, and timers/stopwatches to TOOL054.
- Entered times are calculated locally in the browser and are not sent to a server or Analytics.
FAQ
Frequently asked questions
01How long is 23:30 to 01:15?+
Enable Cross midnight and the interval is calculated as 1 hour 45 minutes.
02Is crossing midnight automatic?+
No. It is OFF by default and must be enabled explicitly when the end time is earlier.
03What time is 12 AM?+
It is 00:00, midnight. 12 PM is 12:00 noon.
04Do I have to use 24-hour time?+
No. You can use the 12/24 conversion feature and choose the result format for arithmetic.
05Can this calculate time zones?+
No. City, UTC, and time-zone conversion belong to TOOL052.