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Day Calculator

Find the exact number of days between any two dates. Calculate calendar days, working days, or even how many days until a future event.

📅 Calculate Days Between Dates
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Days
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Weeks
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Months
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Years
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Hours

How to Calculate Days Between Two Dates

Calculating the number of days between two dates is one of the most common date-related tasks — whether you're tracking a project deadline, figuring out how long until a vacation, calculating someone's age, or determining payment terms in a contract.

Our day calculator does this instantly and accurately, supporting both calendar days (all 7 days of the week) and working days (Monday to Friday only, excluding weekends).

Formula: Days Between Two Dates

The calculation is straightforward: Days = (End Date − Start Date) in milliseconds ÷ 86,400,000 (milliseconds per day). Our tool uses JavaScript Date objects, which correctly handle leap years, month lengths, and daylight saving time transitions.

Common Use Cases

  • Age in days: Use your birthdate as the start date and today as the end date to find exactly how many days old you are.
  • Project timelines: Calculate working days between project start and deadline to schedule tasks accurately.
  • Payment terms: "Net 30" contracts require counting exactly 30 calendar days from an invoice date.
  • Days until an event: Enter today as start date and the event date as end date to find the countdown in days.
  • Lease and contract durations: Calculate the exact length of a rental period or contract in days.

Frequently Asked Questions

Enter the start date and end date in the fields, then click Calculate. The result shows the exact number of days between the two dates, along with equivalent values in weeks, months, and years.
Yes. Check the "Exclude weekends" option before clicking Calculate. The result will show only business days (Monday through Friday), excluding Saturdays and Sundays from the count.
Calendar days count every single day including weekends and holidays. Working days (business days) count only Monday through Friday. Our calculator supports both modes with a simple checkbox toggle.
Yes. Enter your date of birth as the start date and today as the end date, then click Calculate. The result shows exactly how many days you have been alive.
Yes. The day calculator uses JavaScript Date objects which automatically handle February 29 in leap years and all other calendar irregularities accurately.
Enter today's date as the start date and your event date as the end date, then click Calculate. The result shows how many days remain until that event.