Time Calculator
This calculator can be used to “add” or “subtract” two time values. Input fields can be left blank, which will be taken as 0 by default.
Add or Subtract Time
Add or Subtract Time from a Date
Time Calculator in Expression
Time Calculator
This tool allows you to add or subtract two time values. Leave input fields blank to default to 0.
Input Fields
Day | Hour | Minute | Second
Result
Add or Subtract Time from a Date
Use this calculator to adjust a starting time and date by adding or subtracting days, hours, minutes, and seconds. The result will display the new time and date. For calculating the duration between two different dates, use the Time Duration Calculator.
Start Time
February 20, 2025
Select Calendar
Hour | Minute | Second
9 : 41 : 41 AM
Now
Adjustments
Day | Hour | Minute | Second
0 | 0 | 0 | 0
Time Calculator in Expression
This feature lets you add or subtract multiple time values using an expression. Input values must include d (days), h (hours), m (minutes), and s (seconds). Only the + and – operators are allowed.
Example:1d 2h 3m 4s + 4h 5s - 2030s + 28h
Related Tools
- Date Calculator
- Age Calculator
Understanding Time Calculations
Time can be added or subtracted like numbers, but its unique structure requires specific methods for calculations. Below are common units of time:
| Unit | Definition |
|---|---|
| Millennium | 1,000 years |
| Century | 100 years |
| Decade | 10 years |
| Year (average) | 365.242 days or 12 months |
| Common year | 365 days or 12 months |
| Leap year | 366 days or 12 months |
| Quarter | 3 months |
| Month | 28-31 days |
| Week | 7 days |
| Day | 24 hours or 1,440 minutes or 86,400 seconds |
| Hour | 60 minutes or 3,600 seconds |
| Minute | 60 seconds |
| Second | Base unit |
| Millisecond | 10⁻³ second |
| Microsecond | 10⁻⁶ second |
| Nanosecond | 10⁻⁹ second |
| Picosecond | 10⁻¹² second |
Concepts of Time
Ancient Greece
The ancient Greek philosopher Aristotle (384-322 BC) defined time as “a number of movement in respect of the before and after.” He viewed time as a measure of change, requiring motion or change to exist. Aristotle believed time was infinite and continuous, and that the universe always existed. His ideas laid the foundation for later debates about time.
Newton & Leibniz
Isaac Newton described time as absolute, flowing independently of external factors. He called this “duration” and argued it could only be understood mathematically. In contrast, Gottfried Leibniz believed time was relational, existing only in the context of objects and events. Their debate, including Newton’s “bucket argument,” shaped early theories of time and space.
Einstein
Albert Einstein revolutionized the concept of time with his theory of relativity. He introduced the idea of spacetime, connecting space and time into a single framework. Einstein showed that time is relative and depends on the observer’s frame of reference. His work resolved Newton’s bucket argument and redefined our understanding of time and motion.
How We Measure Time
Time is measured using calendars and clocks, both based on the sexagesimal system (base 60). This system, originating in ancient Sumer and adopted by the Babylonians, simplifies calculations due to 60’s high divisibility.
Development of Timekeeping
- Egyptians: Divided the day into 12 parts using sundials and tracked night with 12 stars, leading to the 24-hour day.
- Hipparchus: Proposed equal-length hours based on equinoxes.
- Gregorian Calendar: Introduced in 1582, it corrected inaccuracies in the Julian calendar and is now the global standard.
Early Timekeeping Devices
- Sundials: Used by Egyptians to divide daylight.
- Water Clocks (Clepsydra): Measured time through regulated water flow.
- Hourglasses: Measured specific periods using sand.
- Pendulum Clocks: Invented by Christiaan Huygens in 1656, they were the first highly accurate mechanical clocks.
- Atomic Clocks: Today’s most precise timekeepers, using cesium atomic resonance.
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Time remains one of humanity’s most fascinating and complex concepts, with its measurement evolving alongside our understanding of the universe.