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Days Between Dates Calculator

Calculate the approximate number of days between two dates. Enter start and end dates as year, month, and day. Toggle inclusive or exclusive counting. Note: uses a 30-day month approximation; for exact results use a calendar app.

Written by CalcVault Editorial Team

Fill in the fields above and click Calculate to see your results.

How to use

Use this tool to find exactly how much time exists between two specific dates. Choose your 'Start Date' and your 'End Date' from the calendar inputs.

Optionally, you can toggle 'Include End Date' if you want the final day counted (useful for hotel bookings or event durations). The calculator will instantly output the total number of days, weeks, and years between the two dates.

This is perfect for project planning, counting down to an important life event, or accurately calculating invoice due dates. By providing the exact duration, you can better manage your schedule and avoid any misunderstandings regarding deadlines or contract lengths.

How it's calculated

Days (Exclusive)

(end_year * 365 + end_month * 30 + end_day) - (start_year * 365 + start_month * 30 + start_day)

Approximate days not counting start or end day

Days (Inclusive)

(end_year * 365 + end_month * 30 + end_day) - (start_year * 365 + start_month * 30 + start_day) + 1

Approximate days counting both start and end day

Days Between

(inclusive == 0) * ((end_year * 365 + end_month * 30 + end_day) - (start_year * 365 + start_month * 30 + start_day)) + (inclusive == 1) * ((end_year * 365 + end_month * 30 + end_day) - (start_year * 365 + start_month * 30 + start_day) + 1)

Result based on your selected counting mode

Examples

Jan 1 to Dec 31, 2026 (exclusive)

  • End Day (1–31):31
  • End Year:2,026
  • End Month (1–12):12
  • Counting Mode:0
  • Start Day (1–31):1
  • Start Year:2,026
  • Start Month (1–12):1

Result

  • weeks:4.29
  • years:0.08
  • total_days:30

Between November 1 and December 1 of the same year, there are exactly 30 days (about 4.3 weeks). Including the end date would make it 31 days. Understanding this subtle difference is very important when determining strict legal deadlines or when calculating accurate daily interest for short-term personal loans.

Jan 1 to Jan 31, 2026 (exclusive)

  • End Day (1–31):31
  • End Year:2,026
  • End Month (1–12):1
  • Counting Mode:0
  • Start Day (1–31):1
  • Start Year:2,026
  • Start Month (1–12):1

Result

  • Days Between:30
  • Days (Exclusive):30
  • Days (Inclusive):31

January 2026 has exactly 30 days between January 1 and January 31 (exclusive), or 31 days inclusive. For contract payment terms (e.g., 'net 30'), use the exclusive count — a contract starting Jan 1 is due Jan 30, not Jan 31. This ensures you never miss a payment deadline and maintain a stellar credit profile.

Frequently Asked Questions

What is the difference between inclusive and exclusive counting?

Exclusive counting gives the number of days strictly between the two dates (not counting either the start or end day). Inclusive counting adds 1 to include both the start and end day. For example, Jan 1 to Jan 3 exclusive = 2 days; inclusive = 3 days.

Why is the result approximate?

This calculator uses a simplified formula treating every month as 30 days. This can be off by 1–2 days for months with 28, 29, or 31 days. For exact results, use a dedicated calendar application.

How do I calculate how many days until an event?

Enter today's date as the start date and your event date as the end date. Use exclusive mode to get the number of days remaining before the event.

Does this calculator account for leap years?

Yes, it automatically includes February 29th when calculating the total number of days for periods that cross over a leap year. This ensures that long-term calculations spanning multiple years remain highly accurate, accounting for the extra day seamlessly without requiring any manual adjustment from the user.
CalcVault Editorial Team

CalcVault Editorial Team

Verified Content Team

The CalcVault Editorial Team is a group of finance, health, and mathematics specialists dedicated to producing accurate, bilingual calculator content for Vietnamese and global small business owners. Every formula on CalcVault undergoes rigorous source verification against authoritative bodies including the IRS, CFPB, CDC, WHO, and NIST before publication. Our process includes independent peer review, structured fact-checking, and scheduled content audits to ensure every calculator remains up-to-date with the latest regulatory and scientific standards. We are committed to editorial independence from our advertising partners.

Areas of Expertise

Personal FinanceVietnam Tax & PayrollHealth Metrics & BMIApplied MathematicsBusiness LendingSMB Financial Planning
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