Date to Date Calculator
Enter a start date and end date to get the exact number of calendar days, business days, weeks, months, and years between them, plus total hours, minutes, and seconds. Switch to offset mode to add or subtract days, weeks, months, or years from any date and find the resulting date instantly.
Formula
Worked example
Start: January 1, 2025 (Wednesday). End: April 1, 2025 (Tuesday). Calendar days: 89 (end excluded) or 90 (end included). Business days: 63. Breakdown: 3 months exactly. Total hours: 89 x 24 = 2,136 hours.
How the calculator counts days between dates
The calculator subtracts the start date from the end date to get the number of elapsed calendar days. By default the end date is excluded, which is the standard convention when measuring age or contract length: a one-day stay checking in on Monday and out on Tuesday is one night, not two. Toggle "Include end date" to count both endpoints, which is common in rental agreements and school attendance records. Business days are counted by walking day by day through the interval and counting only Monday through Friday, so the result is always exact regardless of which months or years the interval crosses.
Years, months, and days breakdown
The breakdown field decomposes the total interval into whole years, remaining whole months, and leftover days. This mirrors how humans naturally describe durations: "1 year, 3 months, and 12 days" rather than "482 days." The math works backward: subtract the largest number of whole years that fit, then the largest number of whole months, then count the remaining days. Month lengths vary (28-31 days), so this breakdown can differ slightly from dividing total days by 30.44.
Add or subtract time from a date
The offset mode lets you answer questions like "what date is 90 days from now?" or "what was the date 6 months ago?" Enter a start date, choose the amount and unit (days, weeks, months, or years), and the calculator returns the exact resulting date and its day of the week. Negative numbers go backward. Adding months and years correctly handles calendar edge cases: adding 1 month to January 31 gives February 28 or 29, not an invalid date.
Business days vs. calendar days
Calendar days count every day in the interval, including weekends. Business days (also called working days) count only Monday through Friday. This distinction matters for deadlines and contracts: a court filing due "within 30 calendar days" lands on a different date than one due "within 30 business days." The business day count here excludes weekends but does not exclude public holidays, because holidays vary by country and employer. If your deadline excludes specific holidays, subtract them manually from the business-day count shown here.
Common time intervals in days
| Interval | Calendar days | Business days (approx.) |
|---|---|---|
| 1 week | 7 | 5 |
| 2 weeks | 14 | 10 |
| 1 month (30-day) | 30 | 22 |
| 1 quarter (13 weeks) | 91 | 65 |
| 6 months (approx.) | 182 | 130 |
| 1 year (non-leap) | 365 | 261 |
| 1 year (leap year) | 366 | 262 |
| 2 years | 730 | 522 |
Quick reference for frequently used durations.
Frequently asked questions
How do I calculate the number of days between two dates?
Subtract the earlier date from the later date. In day terms: count every calendar day from the start date up to (but not including) the end date. For example, from January 1 to January 8 is 7 days. This calculator does that subtraction instantly for any two dates you enter.
Should I include the end date when counting days?
It depends on your purpose. For duration or age (how long did something last?) you normally exclude the end date: a project from Monday to Friday spans 4 days of work, because Friday is the finish line, not another working day. For counting occurrences or measuring inclusive periods (how many days did the course run, including the final day?) turn on "Include end date" to add 1 to the total.
What is the difference between calendar days and business days?
Calendar days count every day of the week, including Saturday and Sunday. Business days (working days) count only Monday through Friday. A 14-calendar-day period contains either 8 or 10 business days depending on which day of the week it starts. Use business days when measuring deadlines, lead times, or work durations; use calendar days for personal events, travel, and anything that does not stop for weekends.
Does the calculator account for leap years?
Yes. The underlying calculation uses actual calendar dates, so February 29 is counted automatically in any range that crosses a leap year. A full year from March 1, 2024 to March 1, 2025 counts 366 days because 2024 is a leap year.
How do I find what date is 90 days from today?
Switch to "Add / subtract time from a date" mode, set the start date to today, enter 90 in the amount field, and make sure the unit is "Days." The result date and its day of the week appear immediately. You can also use negative numbers to go back in time.
Why does adding 1 month to January 31 give February 28?
Because February has only 28 days (or 29 in a leap year). When you add one month to a date and the resulting month is shorter than the start month, the date is clamped to the last valid day of that month. This matches standard date arithmetic used by spreadsheets, programming languages, and legal conventions.
How do I calculate how many weeks are in a period?
Divide the total calendar days by 7. A 365-day year contains 52.14 weeks. This calculator shows total weeks as a decimal in the results, so you can read it directly without manual division.