Calculator Tools/Date Calculator
Date Calculator
Calculate date differences and D-Day
Input
Result
Select a date
Date Calculator Guide
Learn how to calculate date differences and add/subtract dates
What is Date Calculator?
The Date Calculator helps you find the difference between two dates or add/subtract time from a date. Perfect for calculating age, project deadlines, event planning, D-day countdowns, and pregnancy due dates.
How to Use
- Choose a mode: Date Difference or Add/Subtract
- For difference: Select start and end dates
- For add/subtract: Enter base date and time to add/subtract
- View results in years, months, weeks, days, and hours
Practical Tips
- Use Date Difference to calculate exact age or days until an event
- Add/Subtract mode is perfect for calculating due dates
- Results show both total days and broken-down format
Accuracy & Limitations
Date calculations account for leap years and varying month lengths. All calculations are performed locally in your browser. Note that results assume the Gregorian calendar system.
Frequently Asked Questions
Does this calculator account for leap years?
Yes, all date calculations properly handle leap years (years divisible by 4, except century years not divisible by 400). February 29th is correctly included when calculating differences that span leap years.
How are months calculated when dates don't align exactly?
When the end day is less than the start day, we borrow from the previous month. For example, January 31 to March 2 is 1 month and 2 days (not 1 month and -29 days). The calculation uses the actual number of days in each month.
Can I calculate the number of business days between dates?
This calculator shows calendar days, not business days. For business day calculations, you would need to subtract weekends and holidays from the total days. Total days are provided so you can make this adjustment if needed.
Why does subtracting months sometimes give unexpected results?
Date math can be tricky with months of different lengths. Subtracting 1 month from March 31 gives February 28 (or 29 in leap years), not a date in February with 31 days. The calculator handles these edge cases according to standard date arithmetic rules.
Is the time displayed in my local timezone?
The date calculator works with date values only (year, month, day) without timezone considerations. The dates you enter and receive are treated as local dates. For timezone-aware time calculations, use our Timezone Converter tool.