Clock Calculator: Time & Duration
1. Calculate Duration Between Two Times
AM
PM
AM
PM
2. Add or Subtract Time from a Clock
AM
PM
Add (+)
Subtract (-)
How to Use the Clock Calculator
This clock calculator is a versatile tool designed for professionals, students, and travelers who need to manage time precisely. Whether you are calculating billable hours, determining the length of a flight, or figuring out what time it will be after a specific duration, this tool provides instant results.
Calculating Time Duration
To find the difference between two points in time, enter the starting hour, minute, and second, followed by the end time. The calculator handles the crossover between AM and PM automatically. If the end time is numerically smaller than the start time (e.g., 10:00 PM to 2:00 AM), the tool assumes the duration spans across midnight into the next day.
Example: If you start a shift at 8:45 AM and finish at 5:15 PM, the duration is 8 hours and 30 minutes.
Adding or Subtracting Hours and Minutes
Adding time is essential for scheduling. If it is currently 2:30 PM and you need to set an alarm for 4 hours and 50 minutes from now, simply use the "Add" function. Similarly, the subtraction function helps you determine start times based on deadlines.
Mathematical Principles of Time Calculation
Time calculation differs from standard decimal math because it uses a sexagesimal (base-60) system for minutes and seconds, and a duodecimal (base-12) or 24-hour system for hours. To calculate manually:
- Step 1: Convert both times into a single unit (total seconds).
- Step 2: Subtract or add the total seconds.
- Step 3: Convert the resulting seconds back into hours, minutes, and seconds.
- Step 4: Adjust for 12-hour AM/PM cycles if necessary.
Common Time Conversion Table
| Unit | Equivalent |
|---|---|
| 1 Hour | 60 Minutes / 3,600 Seconds |
| 1 Minute | 60 Seconds |
| 24 Hours | 1,440 Minutes / 86,400 Seconds |