Organize deadlines and plans: find out how many days have passed or what the exact date will be after a set interval.
Result between dates
Days:
Business Days:
Saturdays and Sundays:
Weeks:
Completed Months:
Completed Years:
Note: The interval includes leap year(s); this has been automatically considered.
Resulting date
Resulting date
The day counter helps you measure the duration between two dates, including
business days and weekends, and find the exact date by
adding or subtracting years, months, weeks, and days. Everything is calculated in UTC
(avoiding timezone/DST impacts) and with Gregorian calendar rules—fast, consistent, and without registration.
Unlike manual counting, the tool automates adjustments like end-of-month,
leap years, and the Include end date mode (+1), in addition to displaying
weeks, completed months, and completed years for reporting.
How to use (step-by-step)
Count days: on the Count days tab, select a Start date and End date. Use “Today” to fill quickly and check Include end date if you need to count both endpoints (+1).
Add period: on the Add tab, choose a Base date and enter values for years/months/weeks/days (any field can be 0). The calculation automatically handles end-of-month cases.
Subtract period: identical to the Add tab, but it removes the entered periods.
Calculate and review: click Calculate. See the card with Days, Business Days, Saturdays and Sundays, Weeks, Completed Months, and Completed Years. If the interval includes a leap year, a note is displayed.
Application Features (highlights)
Three modes of use:Count, Add, and Subtract tabs.
Include end date (+1): explicit control over endpoint counting.
Business days and weekends: automatic calculation in UTC (holidays not included at this stage).
Completed weeks, months, and years: clear metrics for reports and contracts.
End-of-month adjustment: when adding/subtracting months, it falls back to the last valid day when necessary.
“Today” shortcuts: fills base/start/end dates with one click.
Privacy by default: everything is processed locally in the browser.
Accessible and responsive: tabs navigable with keyboard arrows; messages via aria-live.
Understanding the outputs and metrics
Days: total days between dates (a “−” sign if the end date is earlier). With Include end date, +1 is added.
Business Days: number of Mondays to Fridays in the interval.
Saturdays and Sundays: number of weekend days in the interval.
Weeks: integer division of the total days by 7 (quick view).
Completed Months: difference in full months (adjusted by the day of the month).
Completed Years: difference in full years (adjusted by month/day).
Leap year note: automatic notice when the interval includes leap year(s).
How calculations are made
UTC by default: dates are normalized to UTC to avoid timezone/DST effects.
Days: millisecond difference converted to days; option to include the end date.
Weeks: integer division of days by 7.
Completed Months: difference in year*12 + month, subtracting 1 if the target day has not yet been reached.
Completed Years: difference in years, subtracting 1 if the end month/day has not yet passed the start month/day.
End-of-month adjustment: when adding/subtracting months, if the target date doesn't exist (e.g., Feb 31), the last valid day of the month is used.
Business/weekend days: counted by day of the week (0=Sun to 6=Sat), without holidays.
Best practices
Define the criteria first: deciding on Include end date avoids rework.
Consistency in comparisons: maintain the same policy (inclusive/exclusive) when comparing periods.
Check holidays externally: if you need “true” business days, subtract holidays outside the app.
Document parameters: when sharing, state whether the end date was included and which tab was used.
When to adjust your calculation?
Adjust the inclusive mode according to the rules of your context (e.g., stays/tenure). Prefer
UTC for consistent analysis and, when necessary, apply holidays manually
outside the app to get “true business days.”
Frequently Asked Questions (FAQ)
Does counting the same date give 0 or 1 day? With Include end date, it gives 1; otherwise, 0.
Does it consider leap years? Yes. The day algorithm automatically incorporates leap years.
How are “business days” counted? Only Mondays to Fridays; holidays are not subtracted in this version.
Why use UTC? To prevent timezone/DST from altering the total day count.
Can I use it offline? Yes. After loading the page, everything runs locally.
Is my data sent anywhere? No. Nothing is transmitted to servers.
Summary
The day counter offers reliable calculations for durations between dates and add/subtract operations for periods,
with support for business days, weeks, completed months/years, and end-of-month rules—simple, accurate, and private.
Note: educational content; does not substitute for legal, accounting, or professional advice. Adapt practices to your context and local rules.