Time Calculator
This free time calculator can add or subtract time values in terms of number of days, hours, minutes, or seconds. Input fields can be left blank, which will be treated as 0.
Add / Subtract Time
Add to or Subtract from a Date
Time Calculator in Expression
Enter an expression like "1d 2h 3m 4s + 4h 5s - 2030s". Use d, h, m, and s for units.
About Time and its Measurement
Like other numbers, time can be added or subtracted. However, due to how time is defined, there exist differences in how calculations must be computed when compared to decimal numbers.
| Unit | Definition |
|---|---|
| year | 365.242 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 |
Concepts of Time
Various concepts of time have been postulated by philosophers and scientists. Aristotle defined time as a measurement of change or motion. Sir Isaac Newton conceived of absolute time that flows without regard to external factors. In contrast, Gottfried Leibniz believed that time is relational and only makes sense as a way to sequence events. Albert Einstein revolutionized this thinking by introducing spacetime, where space and time are connected. He posited that for observers in different frames of reference, both space and time can change, a concept known as time dilation.
How We Measure Time
Measurements of time are based on the sexagesimal (base 60) numeral system, which originated in ancient Sumer. This system simplifies fractions, as 60 has many divisors (1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, 60), making it ideal for dividing hours into minutes and minutes into seconds. The concept of a 24-hour day is believed to have originated with the ancient Egyptians, who divided the day and night into 12 parts each.