Time Calculator

Time Calculator: Add or Subtract Time and Dates Online

This time calculator can be used to add or subtract two time values. Enter two times in hours, minutes and seconds, choose Add or Subtract, and the result appears instantly, with the total seconds, the decimal hours and a note when the answer moves into the next or previous day. It is perfect for adding up work shifts, working out a finish time, or checking a schedule.

The second calculator lets you add or subtract days, hours, minutes and seconds from any starting date and time. It instantly shows the resulting date and time, the weekday and the ISO date, which helps you plan deadlines, events and reminders. Both calculators are mobile-friendly, fast and accurate. You can choose between 12-hour and 24-hour formats and use the NOW button to fill in the current date and time. They are useful for students, professionals and anyone who needs precise date and time calculations.

Quick answer: 08:30:00 + 02:45:00 = 11:15:00. If the answer passes midnight, such as 23:30 + 01:45, the result wraps to 01:15 on the next day. To work out the time between two times, use the hours calculator instead, which gives the difference rather than a sum.

How to Add and Subtract Time

Time does not use base 10, so you carry at 60 seconds, 60 minutes and 24 hours. To add 02:45 to 08:30, add the minutes first (30 + 45 = 75, which is 1 hour 15 minutes), then add the hours (8 + 2 + 1 = 11), giving 11:15. To subtract, borrow an hour when the minutes are too small. The calculator does all of this for you, and works with seconds too. Here are some examples:

Here is how the common units compare:

Decimal hours are useful for pay and billing. For example, 2 hours 45 minutes is 2.75 hours, because 45 minutes is three quarters of an hour. For working days, the business days calculator can count the days in between.

Adding or Subtracting Time from a Date

The date calculator part of this page starts from the date and time you choose, then moves forward or backward by the days, hours, minutes and seconds you enter. Days follow the calendar, so adding 30 days to January 31 gives March 2, and adding 1 day to February 28, 2028 gives February 29 because 2028 is a leap year. Hours, minutes and seconds count as elapsed time. If your clocks change for daylight saving time between the two dates, the clock reading follows your device’s time zone. To find how many days lie between two dates, try the days between dates calculator, and the date calculator can also add months and years. If you need to convert a time between cities, the time zone converter can help.

12-Hour and 24-Hour Time

The 12-hour clock uses AM and PM, while the 24-hour clock counts the hours from 00 to 23 and is common in many countries and in schedules and timetables. Use the format switch to see results in the style you prefer. This table shows how they match:

Who Uses a Time Calculator?

Employees and managers adding up shifts and breaks, students planning study time, freelancers tracking billable hours, cooks and bakers timing recipes, travelers working out arrival times, event planners scheduling tasks, and anyone who needs to add or subtract time or find a future or past date quickly. Your times and dates are calculated in your browser, and nothing is saved or sent anywhere.

How to Use This Time Calculator

Features