Date Utility
Date
Calculator
Difference
0 days
Mode
Difference
Find the exact difference between two dates in years, months and days, or add and subtract days from any date. The date calculator handles leap years and varying month lengths automatically. Switch between Date Difference and Add/Subtract Days modes to solve any date math problem. Results include total days, weeks and hours for quick reference.
Date Difference
0 years, 0 months, 0 days
Years
0
Months
0
Days
0
Total Days
0
Total Weeks
0
Total Hours
0
How the date calculator works
The date calculator operates in two modes. In Date Difference mode, enter a start date and an end date. The calculator counts complete years from the start to the end, then complete months within the remaining period, then leftover days. This mirrors how you would count on a calendar, correctly handling months with 28, 29, 30 or 31 days.
Total days are computed by finding the millisecond difference between the two dates and dividing by 86,400,000 (the number of milliseconds in one day). Total weeks divide that figure by seven, and total hours multiply it by 24.
In Add/Subtract Days mode, the calculator takes a start date and a number of days. It creates a new date object and shifts it forward or backward by that many days, then displays the resulting date along with the day of the week it falls on.
What you need to know about date calculations
Leap years occur every 4 years, except for century years not divisible by 400. The year 2000 was a leap year, but 1900 was not. February has 29 days in a leap year and 28 in a common year. The date calculator accounts for this automatically when computing differences and when adding or subtracting days.
This calculator counts calendar days, which include weekdays, weekends and public holidays. If you need to count business days only, you would need to exclude Saturdays, Sundays and any applicable holidays from the total. Calendar day counts are useful for deadlines, rental agreements, age calculations and general date math.
When calculating the difference in months, the result depends on which months fall in the range. Moving from January 31 to February 28 counts as one month, even though it is only 28 days. The calculator follows the same convention used by standard calendar counting, where a "month" means advancing the month number by one regardless of how many days that month contains.
Frequently asked questions
How do I calculate the number of days between two dates?
Enter the start date and end date into the date calculator above. It instantly shows the exact difference in years, months and days, plus the total number of days, weeks and hours between them. Leap years and varying month lengths are handled automatically.
How do I add days to a date?
Switch to the Add/Subtract Days mode using the toggle at the top of the calculator. Enter your start date and the number of days to add. The calculator shows the resulting future date, including the day of the week it falls on.
Does the date calculator account for leap years?
Yes. The calculator uses actual calendar logic, so February 29 in leap years is counted correctly. A leap year occurs every 4 years, except for century years not divisible by 400. For example, 2024 is a leap year but 2100 will not be.
How do I subtract days from a date?
Switch to Add/Subtract Days mode, enter your start date and the number of days, then select the subtract option. The calculator shows the resulting past date. This is useful for finding deadlines or past dates relative to a known date.
How many weeks are between two dates?
The date calculator shows total weeks alongside total days and total hours in the Date Difference mode. Total weeks is calculated by dividing the total number of days between the two dates by seven and rounding down to the nearest whole week.
What is the difference between calendar days and business days?
Calendar days include every day — weekdays, weekends and holidays. Business days typically count only Monday through Friday, excluding public holidays. This date calculator counts calendar days. For business day calculations, you would need to exclude weekends and holidays separately.