Time Calculator
Add and subtract durations, adjust dates, and evaluate time expressions
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Time Calculator
Add or subtract time values, adjust a specific date-time by a duration, or compute time expressions using days (d), hours (h), minutes (m), and seconds (s).
➕➖ Add or Subtract Two Time Values
📊 Result
📅 Add or Subtract Time from a Date
📊 Result
🧮 Time Calculator in Expression
📊 Result
📖 Understanding Time
📋 Common Time Conversions
| Unit | Equivalent | In Seconds |
|---|---|---|
| 1 Minute | 60 seconds | 60 |
| 1 Hour | 60 minutes | 3,600 |
| 1 Day | 24 hours | 86,400 |
| 1 Week | 7 days | 604,800 |
| 1 Month (avg) | 30.44 days | 2,629,746 |
| 1 Year (avg) | 365.25 days | 31,557,600 |
💡 Concepts of Time
Ancient Greece
Aristotle (384–322 BC) defined time as “a number of movement in respect of the before and after.” He viewed time as a measurement of change, believed it was infinite and continuous, and argued the universe always did and always will exist.
Newton & Leibniz
Newton argued for absolute time flowing uniformly and mathematically knowable. Leibniz countered that time is relational — only meaningful in the presence of objects and events, serving as a conceptual tool for ordering experiences.
Einstein
Einstein unified space and time into spacetime, showing that measurements depend on the observer’s frame of reference. Moving faster through space leads to moving slower through time, as described by relativity.
How We Measure Time
Modern timekeeping uses calendars and clocks based on the sexagesimal system (base 60), inherited from ancient Sumerians and Babylonians. Base 60’s many divisors make it convenient for subdividing hours and angles.
The Second, Minute & 24‑Hour Day
Egyptians divided daylight into 12 parts using sundials, foreshadowing the 24-hour day. Fixed-length hours became common with mechanical clocks in the 14th century. Minutes and seconds arose from subdividing degrees in Greek astronomy.
Early Timekeeping Devices
Historically, devices such as oil lamps, candle clocks, and water clocks (clepsydras) measured intervals. Hourglasses later provided portable timing. Today, atomic clocks based on cesium resonance provide the most accurate standards — the SI second is defined using cesium radiation, accurate to within 1 second per 300 million years.