Date Calculator
Calculate days, weeks, months, and years between dates. Add or subtract time from any date.
A free online date calculator for computing the time between two dates or adding and subtracting time from a given date. Count days, weeks, months, and years between any two dates, with correct handling of leap years, varying month lengths, and daylight saving time transitions. The calculator also counts business days excluding weekends — and lets you choose which days count as weekends to match your country (Saturday-Sunday, Friday-Saturday, or Thursday-Friday). Add or subtract a number of days from a date to find a future or past date. Useful for project planning, contract deadlines, pregnancy due dates, and visa duration calculations.
How This Calculator Works
Date Difference Calculation: Difference = Date2 − Date1 (in milliseconds, then converted)
The calculator converts both dates to milliseconds since the Unix epoch, subtracts them, and converts the result into days, weeks, months, and years. Leap years and varying month lengths are handled by the JavaScript Date object. Business-day calculations exclude weekends, with configurable weekend days for different countries.
Frequently Asked Questions
How many days are there between two dates?
Enter your start and end dates in the date calculator and it shows the exact number of days between them, plus the breakdown in weeks, months, and years. It also counts business days (excluding weekends) if you need working-day totals. For example, from January 1 to December 31, 2025 is 364 days, or 261 business days (Monday through Friday).
How do I use the date duration calculator?
Enter a start date and an end date. The calculator computes the total duration in days, weeks, months, and years. For example, from March 1 to September 15 is 198 days, or 28 weeks and 2 days, or approximately 6.5 months. The calculator also shows business days (excluding weekends) and lets you configure which days count as weekends for different countries.
How do I use the days between dates calculator?
Enter your two dates and the calculator shows the exact count of days between them. The calculation is exclusive of the end date by default — from January 1 to January 5 is 4 days. You can also count inclusively if needed. The result includes a breakdown in weeks, months, and years, plus a business-day count that excludes weekends.
Why does my date calculation differ by one day from what I expected?
The most common cause is a time zone mismatch. If you count days between January 15 and January 20, the answer depends on whether you mean inclusive counting (6 days including both endpoints) or exclusive counting (5 days between them). This calculator uses exclusive counting by default. Another cause: if your dates span a DST transition, the clock shifts by one hour, which can affect hour-level calculations even though day-level calculations are unaffected.
Does it account for leap years?
Yes. The calculator correctly handles leap years, varying month lengths, and daylight saving time transitions. Leap years add February 29 to the count, and the calculator automatically detects leap years using the Gregorian calendar rule (divisible by 4, except century years which must be divisible by 400).
How do I count business days excluding weekends in different countries?
The calculator lets you choose which days of the week count as weekends. Most countries use Saturday-Sunday, but several Middle Eastern countries use Friday-Saturday, and some use Thursday-Friday. Set the weekend days in the calculator settings to match your region before counting working days.
What can the date calculator compute?
The date calculator can find the number of days, weeks, months, and years between two dates. It can also add or subtract a number of days from a given date to find a future or past date, and count business days excluding weekends and holidays.
Worked Examples
Input: From 2026-01-01 to 2026-09-15
Result: 257 days, 36 weeks 5 days, 8 months 14 days. Business days (Mon–Fri): 184.
Key Features
- Days, weeks, months, years between dates
- Add or subtract time from any date
- Leap year and DST aware
- Business days calculation
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