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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.

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

How to use

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.

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

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

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.

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