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 from a Date
Use this calculator to add or subtract time (days, hours, minutes, seconds) from a starting time and date. The result will be the new time and date based on the subtracted or added period of time.
Time Calculator in Expression
Use this calculator to add or subtract two or more time values in the form of an expression. An acceptable input has d, h, m, and s following each value, where d means days, h means hours, m means minutes, and s means seconds. The only acceptable operators are + and -. “1d 2h 3m 4s + 4h 5s – 2030s” is an example of a valid expression.
Time Units Reference
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. The following table shows some 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 Jan., Mar., May, Jul., Aug. Oct., Dec.—31 days Apr., Jun., Sep., Nov.—30 days. Feb.—28 days for a common year and 29 days for a leap year |
| 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 |
Understanding Time Calculations
Time calculations differ from normal decimal arithmetic due to the non-decimal nature of time units. When performing time calculations, remember:
- 60 seconds = 1 minute
- 60 minutes = 1 hour
- 24 hours = 1 day
- 7 days = 1 week
- 28-31 days = 1 month (depending on the month)
- 365 or 366 days = 1 year (depending on leap year)
These conversions must be taken into account when adding or subtracting time values, especially when units carry over (like when adding 45 minutes to 30 minutes results in 1 hour and 15 minutes, not 75 minutes).