Free Date Calculator Online
Calculate date differences, add or subtract days, and convert between formats.
Enter dates and click Calculate to see results
Usage Examples
How many days until New Year's Eve?
Start: 2026-05-13 End: 2026-12-31
Calculate age from birth date
Start: 1990-06-15 End: 2026-05-13
Trial expires in 90 days — when is that?
2026-05-13 + 90 days
What date was 2 weeks ago?
2026-05-13 − 2 weeks
Project deadline in 6 months
2026-05-13 + 6 months
See all date format variations
2026-05-13 → ISO, US, European, Long, etc.
How to Use Date Calculator
Select a Mode
Choose Difference to compare two dates, Add/Subtract to calculate a future or past date, or Format to convert a date into different formats.
Enter Your Dates
Use the date picker or type a date in YYYY-MM-DD format. For Add/Subtract, specify the amount and unit (days, weeks, months, or years).
View and Copy Results
Results appear instantly. Click the copy button to save the result to clipboard.
Frequently Asked Questions
Date Difference
How do I calculate the difference between two dates?
Select the "Difference" tab, enter a start date and end date using the date pickers, and click "Calculate Difference". The tool shows the difference in years, months, weeks, days, hours, and minutes.
Can I calculate someone's age?
Yes! Use the Difference mode with the person's birth date as the start date and today's date as the end date. The result shows years, months, and days.
Does it count both start and end dates?
No, the difference is calculated as the number of days between the two dates, not inclusive of both dates.
Add & Subtract
How do I add or subtract from a date?
Select the "Add/Subtract" tab, choose a date, select + or −, enter the amount, and choose the unit (days, weeks, months, or years). Click "Calculate" to see the result.
What is 90 days from today?
Use the Add/Subtract mode: set the date to today, select +, enter 90, choose "Days", and click Calculate. The result shows the exact date 90 days from now.
Date Formats
What date formats are supported?
The tool displays dates in ISO 8601 (YYYY-MM-DD), US (MM/DD/YYYY), European (DD-MM-YYYY), Long (Month DD, YYYY), Short (Mon DD, YYYY), and Unix Timestamp formats.
How do I find the week number of a date?
Use the Format mode with your desired date. The output includes the ISO week number and day of year.