Date Difference Calculator
Days, weeks, months, and years between two dates.
Enter any two dates to instantly see the gap in days, weeks, months, years, and business days. Works entirely in your browser with no data sent anywhere.
Calendar vs Business Days
What are calendar days?
Calendar days count every single day between the two dates, including Saturdays, Sundays, and public holidays. This is the straightforward difference you see on any calendar and is useful for general planning, event countdowns, and age calculations.
What are business days?
Business days count only Monday through Friday, skipping weekends. They are used in legal contracts, invoice payment terms (e.g. net 30 business days), project timelines, and HR policies. Note that this calculator does not subtract public holidays, which vary by country and region.
Common use cases
Use this tool to check project deadlines, calculate contract periods, verify invoice due dates, plan event timelines, or determine legal time limits. For legal or financial matters, always confirm business-day definitions with the relevant authority, as holiday exclusions differ.
Difference = End date − Start date Frequently Asked Questions
Does the calculator count the start date or end date?
It counts the days between the two dates exclusively — the start date itself is not counted. For example, from Jan 1 to Jan 3 gives 2 days.
Does it account for public holidays in business days?
No. The business days count skips only Saturdays and Sundays. Public holidays vary by country, state, and year, so you'll need to subtract those manually if required.
What happens if I enter the end date before the start date?
The calculator still works and shows a negative result, indicating the end date is earlier than the start date. This is useful for counting days since a past deadline.
How accurate are the months and years results?
Months are approximated using 30.4375 days per month and years using 365.25 days per year (accounting for leap years). For an exact month or year count, the result may differ by a day depending on the specific months involved.
Can I use this to calculate age?
Yes. Enter your birth date as the start date and today's date as the end date. The years result gives your age in decimal form, and total days gives the exact count.
What is the formula for the Date Difference Calculator?
Difference = End date − Start date. The total days is the absolute difference divided by 86,400,000 milliseconds per day. Business days are counted by iterating each day and checking whether it falls on Monday through Friday.