Date Calculator
Add or subtract days, weeks, months, and years from dates, or find the exact duration between two dates.
100% client-side
No signup
Free forever
Calculate difference between two dates
Add or subtract days from a date
Calculate workdays between dates
Quick Date References
How to Use Date Calculator
How to Use the Date Calculator
- Select calculation type: Choose whether you want to find the difference between dates or add/subtract time from a date.
- Enter start date: Select or type your starting date using the date picker.
- Enter second date or duration: Either enter an end date or specify the number of days/weeks/months/years to add or subtract.
- Optional: Business days only: Check this option to exclude weekends from the calculation.
- Click Calculate: Press the button to perform the calculation.
- View results: See the result with detailed breakdowns (years, months, weeks, days).
Quick Reference
- 1 week: 7 days
- 1 average month: 30.44 days
- 1 year: 365 days (366 in leap years)
- 1 business week: 5 days (Monday-Friday)
- 1 business year: ~260 working days
Features
- Calculate days between any two dates
- Add or subtract days, weeks, months, years
- Business days calculation (excludes weekends)
- Optional holiday exclusion
- Results in multiple units simultaneously
- Leap year aware
- Historical dates supported
- Future dates supported
- Week number calculation
- Day of week display
- Mobile-friendly interface
- Free with no registration
About Date Calculator
Date arithmetic powers project planning, legal deadlines, event coordination, and personal milestones. Our Date Calculator handles both duration finding (how long between dates) and date finding (what date is X days from now).
Calculation Modes
- Days Between Dates: Exact count from start date to end date
- Add Time to Date: Find future dates by adding days, weeks, months, or years
- Subtract Time from Date: Find past dates by subtracting time periods
- Business Days: Count or calculate excluding weekends
- Including/Excluding End Date: Options for fence-post counting
Month Arithmetic Complexity
What's one month after January 31? February 28 (or 29)? What about March 31? Month arithmetic is ambiguous because months have different lengths. We handle this by capping at month end when necessary, matching common business and legal conventions. The same applies to year additions on February 29.
Practical Applications
Contract deadlines often specify "30 days from signing." Pregnancy due dates calculate from last menstrual period. Lease terms add months to start dates. Notice periods combine business and calendar days. Our calculator handles these real-world scenarios accurately.
Frequently Asked Questions
How do I calculate days between two dates?
Enter your start and end dates, and our calculator shows the exact difference in days, weeks, months, and years. We handle month length variations and leap years automatically. You can also see business days only (excluding weekends and optionally holidays).
Can I add or subtract days from a date?
Yes! Enter a start date and specify days to add or subtract. This finds future dates ("what date is 90 days from now?") or past dates ("what was 60 days ago?"). You can add/subtract by days, weeks, months, or years, with correct handling of month-end edge cases.
How are months calculated when dates don't align?
When adding months, if the result would be an invalid date (like March 31 + 1 month), the calculator uses the last valid day (April 30). This is how most software handles it. We clearly show when this adjustment occurs so you can account for it.
How do I calculate business/working days?
Select "Business Days" mode to exclude weekends automatically. You can also add custom holidays or use preset holiday calendars (US Federal, UK Bank Holidays, etc.). This is essential for deadline calculations, project timelines, and delivery estimates.
Can I calculate my age in days?
Yes! Enter your birthdate as the start and today as the end. You'll see your exact age in days, plus weeks, months, and years. Fun fact: 10,000 days is about 27 years - many people celebrate their 10,000th day alive! The calculator can find such milestones.
How do I find what day of the week a date falls on?
Our calculator shows the day of week for any date - past, present, or future. See what day you were born, when a holiday falls, or plan around specific weekdays. Enter any date and get its weekday instantly, along with other date information.