How to use the Date Difference Calculator
- Choose a start date and an end date. If the end date is earlier than the start date, the calculator still works and tells you the gap is in the past.
- Decide whether to include the end date. By default the tool counts the days between the dates. Tick the option if both the first and the last day should be counted — for example, the length of a holiday or a hotel booking that includes both days.
- Read the results in days, weeks, approximate months, exact years-months-days, and weekdays.
What this tool does
Project deadlines, notice periods, subscription terms, pregnancy due dates, visa stays, loan terms and countdowns all come down to the same question: how much time lies between two dates? This calculator gives you every common way of expressing the answer, so you can use the one your situation asks for.
How it works
Days and weeks
The number of days is an exact count of calendar days, including any leap days in the range. Weeks are the days divided by seven, shown with any leftover days (for example, 45 days = 6 weeks and 3 days).
Years, months and days
The years-months-days figure steps through the calendar in the same way people describe durations: first whole years, then whole months, then the remaining days. From 31 January to 1 March is 1 month and 1 day in a non-leap year — the month is counted to 28 February (the last day of February, since February has no 31st), and one more day reaches 1 March.
Calendar months are not equal-sized. Months range from 28 to 31 days, so "months" can be measured two different ways. The Months (approx.) figure divides the day count by the average Gregorian month length of about 30.44 days (365.2425 ÷ 12). The years-months-days figure counts real calendar months. For 1 February to 1 March, the calendar answer is exactly 1 month, but the approximate figure is 0.92 months because February is short. Neither is wrong — they answer slightly different questions. Contracts and legal deadlines almost always use calendar months.
Weekdays
The weekday count includes Monday to Friday only. It does not know about public holidays, which differ by country and region, so subtract those yourself if you are counting working days for a deadline.
Including the end date
From Monday 1st to Friday 5th is 4 days between the dates, but 5 days if you count both Monday and Friday. Use the inclusive option for durations where both the start and end days are "used", such as event days, leave requests or medication courses.
Examples
| From | To | Days | Calendar result |
|---|---|---|---|
| 1 Jan 2026 | 31 Dec 2026 | 364 | 11 months, 30 days |
| 1 Jan 2026 | 1 Jan 2027 | 365 | 1 year |
| 15 Aug 2026 | 26 Dec 2026 | 133 | 4 months, 11 days |
| 1 Feb 2028 | 1 Mar 2028 | 29 | 1 month (2028 is a leap year) |
Tips
- For someone's age, use the Age Calculator, which adds a next-birthday countdown.
- To express progress as a percentage — for example, how much of a 90-day trial has passed — divide the days elapsed by the total with the Percentage Calculator.
- For deadlines stated as "within 30 days", check whether the day of the event counts as day 0 or day 1 — rules differ by organisation.
- Converting a number of days into hours or minutes? The time category of the Unit Converter does that instantly.
Frequently asked questions
How do I count the days between two dates?
Enter both dates above. The calculator counts every calendar day between them, including leap days. Tick "Include the end date" if both the first and last day should be counted.
Why is the number of months approximate?
Months have 28 to 31 days, so converting days to months requires either an average (30.44 days) or counting actual calendar months. The tool shows both: the approximate figure and the exact years-months-days breakdown.
Does the weekday count include public holidays?
No. Public holidays vary by country and region, so the weekday figure counts Monday to Friday only. Subtract any holidays that apply to you.
Can I calculate a date in the past?
Yes. If the end date is before the start date, the calculator shows the same duration and notes that the end date is earlier.
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