Time Calculator

What the calculator works out

The calculator has two modes. In Difference between times mode, it works out exactly how much time separates two points in time, shown in days, hours, minutes and seconds (or in a single combined unit, depending on how large the difference is). In Add / subtract mode, it starts from a given date and time and adds or subtracts a number of years, months, days, hours, minutes or seconds, to work out a new date and time.

How the calculation works

Leap years: The calculation accounts for leap years automatically. February 29th is included in leap years (every four years, except century years not divisible by 400), and this affects how many days fall between two dates.

Months of different lengths: When the result is shown in years and months, each month is counted by its actual number of days (28 to 31), not as an average. That means, for example, "one year and two months" from a given date lands on exactly the same day and month next time round, rather than an approximate number of days.

Time zone: All times are interpreted in your local time zone, the one your device is set to. The calculator doesn't convert between time zones. If you're comparing times across different zones, you'll need to convert them to a shared zone yourself before entering them.

Common uses

The time calculator is often used to work out how many days remain until a deadline or event, how long a job, contract or subscription has lasted, or to work out an exact end date by adding a set amount of time to a start date, for example a 90-day notice period or a 6-month project.

Limitations

The calculation is based on the Gregorian calendar and doesn't account for leap seconds or local calendar variations (for example other calendar systems). Because times are read in your device's local time zone and not converted automatically, double-check the result manually if you're comparing times across a daylight saving change or between different time zones.