NumberTally What Gets Counted
By default this calculator measures the days between two dates: end minus start. January 1 to January 2 is 1 day. Tick “include end date” if you want both endpoints counted (useful for “how many days am I on vacation including the last day”). Business days are Monday–Friday minus any holidays you list — weekends never count, even if a holiday falls on one.
Days = End − Start
Business days = weekdays in range − holidays
Calendar months = full month boundaries crossed
Leap Days Are Automatic
Durations that span a February 29 automatically include it, because the count is done on real calendar dates, not 365-day estimates. From 2024-01-01 to 2025-01-01 is 366 days; from 2025-01-01 to 2026-01-01 it’s 365. The month breakdown counts whole calendar months (Jan 15 → Mar 15 = 2 months) with leftover days shown separately.
Frequently Asked Questions
Does this calculator count the start date, the end date, or both?
By default it counts the days between the dates (end minus start), so Jan 1 to Jan 2 is 1 day. Enable “include end date” to count both endpoints.
How are business days counted?
Monday through Friday, minus any holidays you list in Advanced options. Weekends are never counted as business days.
How are calendar months calculated?
Whole calendar months between the two dates, the same way age is measured: Jan 15 to Mar 15 is exactly 2 months, with any leftover days shown separately.
Can I calculate a duration that includes leap days?
Yes — leap days are included automatically because the math runs on real calendar dates. A span crossing Feb 29 of a leap year counts it.
Does the business-day count include federal holidays?
Tick “Exclude US federal holidays (2025–2026)” in Advanced options and all 11 federal holidays for 2025 and 2026 — with weekend observance shifts — are removed from business-day counts automatically. You can still add your own dates on top.
Can I add business days instead of calendar days?
Yes — switch to “Add / subtract days”, tick “Business days only”, and the result skips weekends plus any listed or federal holidays. Useful for deadlines like “5 business days from today”.
Is my data stored anywhere?
No. Every calculation happens in your browser; nothing is sent to a server or stored.