Number of Days Between Dates Calculator
Calculate the exact number of days, weeks, or months between two dates. Useful for deadline tracking, project planning, and date math.
📅 Dates📐 Days Between = End Date - Start Date
Start year
Start month (1-12)
Start day
End year
End month (1-12)
End day
Please enter valid values.
Formula & Reference
| Variable | Formula | Units |
|---|---|---|
| Number of Days Between Dates Calculator | Days Between = End Date - Start Date | days |
Step-by-Step Examples
Example 1
Year to Year
Jan 1, 2025 to Dec 31, 2025.
- 365 days (2025 is not a leap year)
- 52 complete weeks + 1 day
✓ 365 days
Example 2
Project Deadline
Jan 15, 2025 to Mar 31, 2025.
- 75 days | 10.7 weeks | 2.46 months
✓ 75 days
Example 3
Leap Year
Feb 1, 2024 to Feb 1, 2025.
- 366 days (2024 was a leap year)
✓ 366 days
Real-World Applications
Project Managers
Track project duration and deadline proximity.
Business
Calculate contract periods, notice periods, and deadlines.
Homeowners
Calculate remaining mortgage term or maintenance intervals.
Legal
Calculate statute of limitations and legal notice periods.
Common Mistakes to Avoid
⚠️
Off-by-one errors
When calculating inclusive vs exclusive: Jan 1 to Jan 31 is 30 days exclusive (counting gaps) or 31 days inclusive (counting all days including start and end).
⚠️
Not accounting for leap years
2024 was a leap year (366 days). Date calculations spanning February in leap years must account for Feb 29.
⚠️
Business days vs calendar days
For legal and business purposes, you may need business days (excluding weekends and holidays), not just calendar days.
Frequently Asked Questions
How many days in each month? ▾
30 days: April, June, September, November. 31 days: January, March, May, July, August, October, December. 28 or 29 days: February (29 in leap years - divisible by 4, except centuries must be divisible by 400).
When is the next leap year? ▾
Leap years: 2024, 2028, 2032, 2036... Every 4 years, except century years not divisible by 400. 2100 will NOT be a leap year; 2000 was (divisible by 400).
How many days until Christmas? ▾
This is date-specific. Christmas is December 25 every year. Use this calculator with today's date as start and December 25 as end.
How many working days in a year? ▾
Approximately 260 working days (52 weeks x 5 days). Subtract federal holidays (11 per year) = ~249 working days. Companies with additional holidays may have 245-250 working days.
How to count days for a legal deadline? ▾
Varies by jurisdiction. Federal courts: Rule 6 of FRCP - count from the day after the triggering event. Some rules exclude weekends/holidays. Always verify the specific counting method in the applicable rules.