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Workdays & date math

Date Calculator: Add Days, Subtract, Days Between Dates & Business Days

Add or subtract days, weeks, months, or years from any date, or measure the gap between two dates. Toggle weekends and US, UK, or Canada holidays off for a business-day count. Everything runs in your browser.

By Jeff Beem

Updated

01

Mode

Operation

Result

Wednesday, May 27, 2026

Totals

Months0 Months
Weeks0 Weeks
Days0
Hours0 Hours
Minutes0 Minutes
Seconds0
02

How it works

Month-end and leap-year handling

The browser’s calendar rules handle uneven months and Feb 29, so add/subtract and span math stay consistent with real dates.

Why manual counts go wrong

Off-by-one skips, different weekend rules, and observed holidays on substitute weekdays are the usual reasons paper counts disagree with a machine count.

Business-day counts

Weekend and holiday exclusions apply only in Difference mode and change the working-day total, not the calendar span breakdown.

Switch to Difference to configure exclusions.

US federal holidays

Observed dates (Fri/Mon substitutes) are what the list removes, often where hand counts drift.

UK bank holidays

England & Wales observed bank holidays, including substitute weekdays when the statutory day falls on a weekend.

DST

This tool counts calendar dates, not clock-hour spans across DST. Use a time calculator for exact clock deltas.

Pick the mode first

Same tool answers “add days to a date,” “subtract days from a date,” and “how many days between two dates,” depending on the mode. Add / subtract moves one anchor forward or back by years, months, weeks, or days. Difference fixes two endpoints and measures the gap. Pick the mode that matches your question; fields and toggles follow.

Fast choices

Counting forward from a known date

Need to find the date 30 or 90 days after a contract is signed, a lease starts, or someone gives notice? Use Add / subtract. Pick the start date, type the number of days, and hit Add. Save the answer somewhere your future self will actually find it (a calendar reminder, not a sticky note).

How long until launch?

Counting down to a launch, deadline, or trip? Use Difference. Put today’s date in the start field and your target date in the end field. The result block shows the gap in years, months, and days, plus the total day count. To count only weekdays, stay in Difference mode and turn on Exclude weekends.

Workdays only

Want a working-day total instead of total elapsed days? In Difference mode, turn on Exclude weekends so Saturdays and Sundays drop out. If your team also takes federal holidays off, turn on Exclude holidays and pick the region (US federal, UK England and Wales, or Canada federal) that matches your office calendar.

Which holiday set should I pick?

Three holiday lists are built in: US federal, UK England and Wales bank holidays, and Canada federal. Pick whichever matches the days your office is actually closed, not the one that sounds international. Provincial, state, or company-specific holidays aren’t in the lists, so adjust the result by hand if those matter for your count.

Date Calculator: Add, subtract, and compare dates

Add days to a date or subtract days. Measure days between two dates. Optional weekends and US, UK, or Canada holidays for business-day totals.

What This Date Calculator Does

This date calculator covers the phrases people type into search: add days to a date, subtract days from a date, and how many days are between two dates. In Add / subtract, start from one calendar day and roll forward or back by years, months, weeks, or days until you reach the landing date you need (notices, renewals, “60 days from signing,” and similar). In Difference, fix two endpoints and measure how far apart they are in calendar time. Turn on optional weekend stripping and holiday stripping (US federal, UK England and Wales bank holidays, or Canada federal) when the question is really “how many business days” inside that span. You get weekday names, span breakdowns, and working-day totals when exclusions apply. It does not replace clock arithmetic across time zones or shift schedules; for hours and minutes on the same day, use a time calculator. For age-style wording between birthdays, use an age calculator. When you start from two birth dates and want the gap between people rather than one lifespan, use the Age Difference Calculator. Everything runs locally in your browser.
Why bother with a dedicated tool? Because spreadsheets lie kindly. They’ll happily add 30 to a date cell and call it a month when your contract means “calendar month.” Because counting business days means choosing what to exclude, and the right answer depends on whose office calendar you’re using. This page keeps those toggles in plain sight. Because arguing whether Friday counts should happen once, in writing, not every quarter when someone reruns the numbers in their head. Short version: if the answer must match how HR, legal, or shipping actually counts, use the same rules every time. That’s the point.

Quick Examples: Add Days, 60 or 180 Days, Biweekly Steps

These mirror common searches without needing different software. Add days: Add / subtract mode, pick the start date, type the day offset, tap Add. 60 days from a date or 180 days before a date: same mode; enter 60 or 180 in the days field, then Add or Subtract depending on whether you need forward or backward. How many days between two dates: Difference mode with start and end; read total calendar days (and turn on exclusions if you need working days). Biweekly: treat “every two weeks” as adding 14 calendar days from each result when you need the next occurrence. If someone says “biweekly” but means twice per calendar week, that is a different rule set; clarify before you stake a deadline on it.

How the Math Works

Whole-day gaps boil down to milliseconds between midnight anchors, then floor-divided by the length of a solar day in milliseconds. In symbols: Days=⌊tend−tstart86,400,000⌋\text{Days} = \left\lfloor \frac{t_{\text{end}} - t_{\text{start}}}{86{,}400{,}000} \right\rfloor That sounds colder than it feels. Here’s the human version. Calendars are messy. Months aren’t equal. February steals or adds a day. When you add “one month” inside the tool, the stepping follows the same calendar rules your browser uses for Date objects, which is why January 31 plus one month doesn’t pretend February has 30 days.
Business-day counts start from the calendar span you asked for, then drop weekend dates and any holiday dates that fall inside the selected region’s list. Think of it as subtracting rows from a printed calendar when those rows are Saturdays, Sundays, or marked holidays. Weekend skipping uses weekday arithmetic instead of walking day by day, which keeps large ranges fast. Holiday hits come from a precomputed set for the region you picked.
DST doesn’t change the integer day index unless you cross midnight on the civil calendar; we’re not measuring 23-hour or 25-hour clock days here. If you need that precision, you’ve left “date math” and entered “timestamp math.”

Tiny example

Picture 14 calendar days between a Monday start and a Monday two weeks later. Raw count: 14. Throw out weekends inside that window and the working-day number drops. Throw out a federal Monday holiday and it drops again. Same two anchors, three different answers depending on the question. The UI keeps those stories separate so you don’t merge them by accident.

How to Use This Calculator

Use the mode switch at the top. Add / subtract needs a base date and offset boxes. Leave unused offsets at zero. Pick Add or Subtract so the direction matches your paperwork. Read the resulting date and weekday in the results block. For span questions, choose Difference, type the earlier boundary in start and the later boundary in end (swap mentally if you pasted them backwards). The breakdown shows years, months, and remaining days the way people narrate elapsed time, plus total calendar days. Enable Exclude weekends inside Difference when “business days” means Monday through Friday. Enable Exclude holidays and choose US federal, UK England and Wales, or Canada federal when your office follows those closures. The business-day total updates when either toggle changes. If exclusions are grayed out, you’re still in Add / subtract; flip to Difference first. When you need only “how many Tuesdays until…” style trivia, a day of the week calculator can name weekdays fast, but this tool carries the counting logic you need for contracts.

Why Your Business-Day Count Doesn’t Match the Wall Calendar

People love arguing this one. Usually they counted weekends twice, forgot whether the delivery date itself counts, or used a holiday list from the wrong country. Observed holidays make it worse: when Christmas lands on Saturday, many offices take the Friday or Monday instead. This calculator uses its built-in tables for the region you pick, not your paper desk calendar from five years ago. If your employer uses a custom list, treat the built-in total as a baseline and adjust manually. Still beats counting rows with a highlighter.
Another trap: mixing “how many weekdays between” with “how many business days until.” One cares about interior weekdays only; the other often cares whether the deadline day itself is workable. Different nouns, different math. Say which story you need before you paste dates into email. Your colleagues will act like this distinction is obvious. It is not.

End-of-Month Surprises When You Add Months or Years

Month math punishes optimism. Add a month to the 30th of a short month and you might land earlier than you pictured. Add years across a leap day and February reminds you it exists. The tool mirrors JavaScript calendar stepping so it matches what most web apps do, which is what you want when you sanity-check software dates. If your lease uses literal “calendar months,” confirm against the output instead of mentally adding 30 days.

Holiday Regions: What Each Option Really Means

US federal focuses on federal observances in the common list people mean when they say “bank holiday” in the US. UK England and Wales follows bank holidays for that jurisdiction, not Scotland’s separate list. Canada federal tracks federal statutory holidays nationwide; provinces can differ. Pick the closest match. None of these replace legal advice for filing deadlines; they replace guesswork for everyday scheduling.

Date Calculator FAQ

How do I add days to a date?

Choose Add / subtract, set your start date, enter the number of days in the days field (and months or years if needed), then tap Add. The result shows the new calendar date and weekday.

How do I subtract days from a date?

Stay in Add / subtract. Enter the same offsets, then tap Subtract instead of Add. That rolls the calendar backward by the amounts you typed.

How many days are between two dates?

Switch to Difference. Put the earlier date in start and the later date in end. The tool shows total calendar days plus a years/months/days breakdown. Turn on weekend or holiday exclusions only if you want a working-day style count rather than raw calendar days.

How do I calculate 60 days from a date (or 180 days)?

Use Add / subtract. Pick the anchor date, type 60 or 180 in the days box, leave other offsets at zero unless your rule uses months, then tap Add. For “180 days before,” use the same offset with Subtract.

How do biweekly (every two weeks) dates work?

Biweekly usually means “every 14 calendar days.” In Add / subtract, add 14 days repeatedly from each landing date to step forward. If your policy uses business weeks instead, confirm whether weekends count with whoever owns the rule.

Why is my business-day count different from my manual count?

Hand counts skip rules. Three things bite people: counting the start or end day differently, forgetting weekends, and forgetting that holidays sometimes move when they fall on a Saturday. This tool applies one consistent rule set so you can argue with the spreadsheet, not with yourself.

How do I calculate 90 days from today?

Stay on Add / subtract. Leave the base date as today unless the contract names another anchor. Put 90 in the days box. Hit Add. Done.

How do I count business days between two dates?

Switch to Difference. Enter start and end. Turn on weekend exclusion if Saturdays and Sundays should not count. Add holiday exclusion if US federal, UK bank, or Canada federal calendars match your office. The working-day line is the one HR usually cares about.

What happens if the end date lands on a weekend or holiday?

Calendar math doesn’t magically erase a weekend on the calendar. The span in plain days stays what it is. Flip on exclusions only if you’re asking how many workdays fall inside the range. Different question, different number.

Does daylight saving time affect the date count?

No for day-based answers. We stay on calendar dates in your local zone, so spring-ahead doesn’t shrink the count by a day. Need hour-by-hour deltas across a DST jump? Use a time-duration tool instead.

What happens when I add one month to a date near the end of the month?

Months are uneven. The code follows normal JavaScript calendar stepping, same as most browsers. That means January 31 plus one month lands in February according to those rules instead of pretending every month has 30 days.

Which holiday calendars can I exclude?

US federal, UK England and Wales bank holidays, or Canada federal. Choose the set that matches real closures where you work. Provincial or state quirks may still need a manual tweak.

Time & Date Reference Note

Informational Use: These tools use standard date/time algorithms and your browser’s timezone data (IANA). Results are intended for general reference and planning only.

Verification Recommended: Time zone rules and daylight saving changes vary by region and year. For critical scheduling, payroll, or legal deadlines, confirm results with official sources.

Local Verification: Always confirm times, dates, and business-day counts with official sources or qualified professionals when stakes are high.

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