Days Calculator

Count days, add days, and subtract days in one place. This days calculator counts the days between two dates, adds or subtracts a number of days, weeks, months, or years from a starting date, and breaks the result into working days and weekend days. It shows the result date with its day of the week, so you can tell at a glance whether a deadline lands on a Monday or a Saturday. Everything updates instantly in your browser.

Days are the everyday unit of planning. People count days until a vacation, days left in a school term, days since an event, and days to add to reach a deadline. The hard parts are always the same: month lengths change, February gains a day in leap years, weekends interrupt work counts, and the question of whether the first and last days both count changes the answer by one. This calculator states its rules on the result, counts in whole calendar days, and separates calendar days from business days, so the answer is never ambiguous.

The default view counts the days in the full calendar year 2026, from January 1 to December 31, a span of 364 days, and at the same time adds 90 days to October 29, 2026, landing on January 27, 2027. Both results are visible the moment the page loads. Use the presets for common jumps, such as 7, 30, 60, 90, and 365 days, and use the working day options when the question is about work, school, or business rather than calendar time. The sections below explain counting rules, working day counting, month-end behavior, and the preset jumps people use most often.

How to Use the Days Calculator

This calculator has two jobs, and both are always visible. The top half counts days between two dates. The bottom half adds or subtracts a number of days, weeks, months, years, or business days from a starting date. You do not need to switch modes or hide one job to use the other. Enter dates in either half and both results update.

1. Count a span: enter a start date and an end date in the top half. Read the big day count first, then the table for weeks, business days, weekend days, and hours.
2. Tick include the end date only when both days count. Leave it unticked for elapsed time and countdowns. Tick it for vacation days used, course days, and hotel-style date coverage.
3. Move a date: enter a starting date, a number, a unit, and a direction in the bottom half. Days and weeks are exact. Months and years are calendar units. Business days skip weekends.
4. Use a preset for a common jump. The preset buttons set the number to 7, 30, 60, 90, or 365 days, set the unit to days, and set the direction to add, in one tap. Change the number afterward if you need a nearby value, such as 45 or 100 days.
5. Check the weekday of the result. A deadline that lands on a Saturday may need to move to Friday or Monday in practice, even though the calendar date is correct.

If a date is blank or impossible, the calculator asks for a valid date instead of guessing. If the number is blank, it is treated as zero, and the result date is the starting date itself. If the end date is earlier than the start date in the top half, the gap size is still reported, with a note about the direction, so a swapped pair never produces a confusing negative count.

Counting Days by Hand Without Errors

Hand counting works if you count in blocks. Count whole months first, then leftover days, and write each block down. From March 10 to May 10 is two months. From May 10 to May 24 is 14 days. The total is two months and 14 days, or 75 days in a common year, because March has 31 days and April has 30. The trap is counting the start date as day one and the end date as an extra day at the same time, which adds one day twice over. Pick one rule, exclusive or inclusive, and use it for the whole count. The calculator shows both, so you can see the one-day difference and pick the right one for your purpose.

When to Count in Days, Weeks, or Months

Days are best for short spans and deadlines under three months. Weeks are best for schedules, school terms, and work plans, because work repeats weekly. Months are best for contracts, rent, subscriptions, and pregnancy timelines, because those promises are stated in calendar months. Years are best for long spans, anniversaries, and age-related planning. The calculator reports days, weeks, and an approximate month count together, so you can move between units without re-entering dates. For an exact calendar breakdown in years, months, and days, use the date difference calculator, which gives that breakdown as its headline result.

What Counts as a Day

A day in this calculator is a calendar day, from one midnight to the next, counted in Coordinated Universal Time so daylight saving time never adds or removes a day. That is the right unit for dates, deadlines, and anniversaries. It is not the same as a 24-hour period measured from a time of day. From 11:00 PM on Monday to 1:00 AM on Tuesday is two hours, but it crosses one midnight, so it spans two calendar dates. From 1:00 AM on Monday to 11:00 PM on Tuesday is 46 hours, but it spans the same calendar gap as the first example when counted in whole days. If you need exact hours between clock times, use the time calculator, which handles times of day, overnight spans, and breaks.

The exclusive count is the number of midnights between two dates. The inclusive count is the number of calendar dates covered, including both end dates. The difference is always exactly one. That one day is the source of most date disagreements, and the calculator prevents it by showing both counts labeled, every time, in the same table. When you share a result, share the label too: say 301 days exclusive, or 302 days inclusive, not just 301 days, so the other person knows which count you mean.

• Elapsed time: use the exclusive count. How long ago was March 1? Count midnights since then.
• Days used: use the inclusive count. How many vacation days did a trip use? Count both the first and last day.
• Countdowns: use the exclusive count. How many days until the trip? Count the midnights still to pass.
• Nights away: use the exclusive count. A trip from Friday to Sunday is two nights, even though it covers three calendar dates.
• Course days: use the inclusive count when the course meets on both the first and last day.

Daylight Saving Time and Date Counts

Daylight saving time moves clocks by one hour in spring and fall in most of the United States, but it never changes a calendar date count. March 9, 2026, is one calendar day after March 8, even though the spring-forward weekend has only 23 hours on the clock. November 2, 2026, is one calendar day after November 1, even though the fall-back weekend has 25 hours. Counting in Coordinated Universal Time, as this calculator does, removes the clock shift from the date math entirely. If you are counting hours across a daylight saving change, use a clock tool and check the local time zone rules, because the hour count and the day count will differ by one hour on those weekends.

Working Days and Weekend Days in a Range

Working days, also called business days, are Monday through Friday in the United States. Weekend days are Saturday and Sunday. In any inclusive range, business days plus weekend days equal the inclusive day count, which gives you a built-in check: if the two numbers do not add up to the inclusive total, something was miscounted. The calculator counts both end dates when they fall on weekdays for business days, and when they fall on weekends for weekend days, so the check always holds.

A full common year has 261 business days and 104 weekend days, and a full leap year has 262 business days when the leap day is a weekday, as it was in 2024. Those totals assume no holidays are subtracted. Holidays fall on weekdays in most years, so the number of actual working days in a year is lower: subtract the weekday holidays your employer observes from 261 or 262 to get the real working year. Federal holidays alone remove about eleven weekday days in a typical year, leaving about 250 working days, though the exact number shifts with the calendar.

Adding Business Days Step by Step

Adding business days means stepping forward one calendar day at a time and counting only weekdays. Adding five business days to a Friday lands on the following Friday, not the following Wednesday, because Saturday and Sunday are skipped. Adding one business day to a Friday lands on Monday. Adding zero business days lands on the starting date itself, even if the starting date is a weekend, because no step is taken. The calculator follows exactly that stepping rule, starting the count on the next day, not on the starting date. That starting rule matters: some tools count the starting date as day one, which shifts every result by one day, so always check whether a tool counts from the next day or from the starting date.

Holidays and Working Day Counts

Holidays are the one part of working day counting that no calculator can do for you without a list. Federal, state, court, school, and employer holiday lists all differ, and a holiday that falls on a weekend is already excluded as a weekend day, so it must not be subtracted twice. The safe method is: count business days with this calculator, list the holidays in your range that fall on weekdays, and subtract that number. For federal holidays, check the official schedule for the year. For school holidays, check the district calendar. For court deadlines, check the court calendar, because courts sometimes observe holidays that employers do not, and vice versa.

Adding and Subtracting Days: Presets That Matter

Certain day counts come up so often that they deserve preset buttons. Seven days is one week. Fourteen days is two weeks, the length of many notice periods and pay periods. Thirty days is the classic notice period, payment term, and return window. Sixty days is a common trial, review, and application window. Ninety days is a quarter of a year, a common probation, visa, and warranty period. One hundred days is a milestone count used in schools and in celebrations. Three hundred sixty-five days is one common year. The preset buttons cover the most common jumps, and the number field covers everything else.

Notice that the 30-day jump from October 29 lands on a Saturday. In practice, a deadline on a Saturday often moves to the next business day, or the rule itself says the deadline moves to Monday if it falls on a weekend. That weekend shift is a rule about practice, not about calendar math, so the calculator reports the true calendar date and leaves the shift to the rule that governs the deadline. Always check whether your rule moves weekend deadlines, and if it does, apply the shift after you calculate the calendar date.

The 100-Day Milestone

Schools in the United States celebrate the 100th day of school, usually in late January or early February, with counting activities for young children. The 100th day is counted inclusively in most schools: the first day of school is day one, so the 100th day is 99 days after the first day, not 100. Families also mark 100 days since a birth, a wedding, or a move, and the same inclusive question applies. If you mean 100 days after an event, use add mode with 100 days. If you mean the 100th day counting the event day as day one, add 99 days. The calculator shows the exclusive count plainly, so you can pick the right one and state it.

30, 60, and 90 Day Windows in Business

Payment terms of net 30, net 60, and net 90 mean payment is due 30, 60, or 90 days after the invoice date, counted in calendar days unless the contract says business days. Return windows of 30 days usually mean 30 calendar days from the purchase or delivery date. Trial periods of 30, 60, or 90 days usually start on the signup date and end on the date that many days later, with the last day included or excluded depending on the terms. In every case, the calendar date is only half the answer. The other half is the counting rule in the terms, and the calculator gives you the calendar date so you can apply the rule to it.

Months, Years, and the Month-End Snap

Adding months is calendar arithmetic, not day arithmetic. Adding one month to March 15 gives April 15, because the day of the month is kept. Adding one month to January 31 gives February 28 in a common year, because February has no 31st day, so the result snaps to the last day of February. Adding one month to January 30 gives February 28 as well in a common year, and adding one month to January 29 gives February 28 in a common year but February 29 in a leap year. The snap rule is the only sensible rule, because the alternative, rolling over into March, would make January 31 plus one month land in March, which no one means by one month later.

Adding years follows the same snap rule for February 29. Adding one year to February 29, 2024, gives February 28, 2025, because 2025 has no February 29. Adding four years to February 29, 2024, gives February 29, 2028, because 2028 is a leap year. For birthdays, the snap rule matches the common practice of celebrating on February 28 in common years, and the age calculator uses the same rule, so the two tools agree on leap day birthdays.

Adding Months Repeatedly

Adding months repeatedly can drift if you snap and then keep adding from the snapped date. January 31 plus one month is February 28. Adding another month to February 28 gives March 28, not March 31, because the day of the month is now 28. If you want the last day of each month, add months from the original date each time, or state the rule as the last day of the month. Subscription billing, rent due dates, and loan schedules all have rules for this drift, and the rule is usually stated in the contract. The calculator adds from the date you enter, one operation at a time, so a repeated series should be built by adding the total months to the original date, not by chaining snapped dates, unless chaining is what the contract requires.

Years and Anniversaries

Adding years keeps the month and day, with the February 29 snap as the only exception. A wedding anniversary, a work anniversary, and a company founding date all move forward by calendar years, not by 365-day blocks, because the anniversary is the same calendar date in the new year. A ten-year anniversary of October 29, 2026, is October 29, 2036, which is 3,653 days later, not 3,650, because the span includes leap days in 2028, 2032, and 2036. Counting anniversaries in days without accounting for leap days understates the span by one day per leap year, which is why the calculator counts calendar years separately from total days.

Counting Days Across Years and Leap Years

Spans that cross a year boundary need care with the year length. A common year has 365 days. A leap year has 366. A span from January 1, 2026, to January 1, 2027, is 365 days, because 2026 is a common year. A span from January 1, 2024, to January 1, 2025, is 366 days, because 2024 is a leap year. A span from March 1, 2024, to March 1, 2025, is 365 days, because the leap day of 2024 falls before the span starts. The leap day only counts when February 29 falls inside the span, not merely when a leap year is named in the span.

The Gregorian leap rule is worth memorizing for long spans: divisible by four, except century years, which must divide by four hundred. The year 2000 was a leap year. The year 2100 will not be. For spans within a normal lifetime, the century exception rarely matters, but for spans that cross 2100, it matters by exactly one day, and a one-day error in a deadline is still an error.

Day Counts for School Terms and Semesters

A school semester is usually counted in weeks and instructional days, not in calendar days. A 15-week semester has about 75 instructional days if classes meet five days a week, minus holidays and breaks. A 16-week semester has about 80. The calendar span from the first day to the last day is longer, because it includes weekends and breaks. Use the business day count for instructional days, subtract the holidays on the school calendar, and use the calendar count for the elapsed span. Both numbers belong in a course plan, labeled, so students and parents know which is which.

Worked Examples: Trips, Deadlines, and Anniversaries

Worked examples show how the same tool answers very different questions. Each example states the counting rule, so you can reproduce it in the calculator and check the result.

The trip example is the most common use of a days calculator. Fifty-two days is seven weeks and three days, which is a useful planning horizon: book flights now, book hotels in two weeks, arrange a passport check in four weeks, and pack in the final week. The business day example is the most common use in offices. Ten business days from a Friday is two full work weeks later, landing on a Friday, which is intuitive once you see the weekends skipped. The anniversary example shows why calendar years and day counts must stay separate: ten calendar years is not ten times 365 days.

Example: A 45-Day Project

A project that starts on Monday, March 2, 2026, and runs for 45 calendar days ends on April 16, 2026, a Thursday. The same project counted in business days runs for 45 working days, which is nine work weeks, ending on May 1, 2026, a Friday, if no holidays intervene. The calendar version and the business version differ by sixteen days, which is the number of weekend days in nine weeks. A plan that states 45 days without saying which kind of day is underspecified by more than two weeks. Always state calendar or business, and write the end date down, so the plan can be checked.

Example: Counting Backward to a Start Date

A wedding on June 20, 2027, with a venue that needs six months of notice, a dress that needs four months, and invitations that need eight weeks, gives three backward dates: December 20, 2026, for the venue, February 20, 2027, for the dress, and April 25, 2027, for the invitations. Each date comes from subtract mode with a different unit. The earliest date is the date planning must start, and the latest date is the last action that can still be taken on time. Backward counting turns a single deadline into a dated checklist, which is far more useful than a single countdown number.

Days and Time Zones

Calendar days do not depend on time zones for most planning, because a date is a date in the place where the event happens. A flight that leaves New York on October 29 and arrives in London on October 30 spans one calendar day in each place, and the flight duration in hours is a separate question for the time calculator. A deadline set in one time zone and counted in another can shift by a day at the boundary, so deadlines should always state the time zone and the local date. The official time in the United States is kept by the National Institute of Standards and Technology, and the time.gov site shows the official time for United States time zones, which is the reference to use when a deadline states a time of day as well as a date.

For date-only counting, this calculator uses Coordinated Universal Time internally, so the result is the same no matter where you open the page. That is the correct behavior for a date tool. If you need to know what time it is now in another city, or how many hours separate two clock times in different zones, use a world clock or a time zone tool, not a days calculator. The day count will be right either way, but the clock time needs the zone.

International Date Line

The International Date Line is the boundary where the calendar date changes by a full day. Crossing it westward skips a calendar date, and crossing it eastward repeats a calendar date. Travelers who cross the date line gain or lose a day on the calendar, even though the flight duration in hours is unchanged. For planning, record dates in local time at each location, and count days in each location separately. A trip that leaves on October 29 and arrives on October 31, after crossing the date line, is not a two-day trip in flight time, and the day count must be read with the zone in mind.

Days in Health, Pregnancy, and Recovery Planning

Day counts matter in health planning, where intervals are often stated in days, not months. A medication taken every 30 days, a follow-up in 14 days, and a recovery period of six weeks are all day counts, and each one should be calculated with add mode from the starting date. A pregnancy timeline is counted in weeks and days from a known date, and the pregnancy due date calculator uses the standard 40-week rule to give a due date and a week-by-week timeline. For general health tracking, your body mass index and daily water target are checked on a daily basis, and a days calculator helps you count the days in a habit streak or a training block.

• Medication schedules: count in days from the start date, and set a reminder on the result date, not on a rounded month date.
• Follow-up appointments: a follow-up in 14 days is two weeks later, on the same weekday, which is easy to remember and easy to check.
• Recovery periods: a six-week recovery is 42 calendar days, which includes weekends, because recovery continues every day.
• Habit streaks: count inclusively if the first day counts as day one, and state the rule when you share a streak.
• Training blocks: count in weeks for training, and in days for rest days, so the weekly rhythm stays visible.

Counting Days for a Habit or Streak

A streak that starts on January 1 and is still going on January 31 is 31 days inclusive and 30 days exclusive. Most streak trackers use the inclusive count, because the first day is day one. If you report a streak, state the start date and the counting rule, so the number can be checked. A 100-day streak counted inclusively ends 99 days after the start date. A 100-day streak counted exclusively ends 100 days after the start date. The one-day difference is small, but it is the difference between celebrating on the right day and celebrating a day early.

Days Calculator Accuracy and Limits

This calculator is exact for Gregorian calendar dates, counting whole days in Coordinated Universal Time. It handles leap years with the full century rule, month ends with the snap rule, business days with the Monday to Friday stepping rule, and reversed dates by reporting the gap size with a direction note. The result is as exact as the dates and the number you enter. A wrong start date or a misunderstood counting rule will produce an exact answer to the wrong question, so check the inputs and the rule before you trust the result.

The limits are about holidays, clock times, and legal rules. Holidays are not subtracted, because no single list fits every case. Clock times are ignored, because this is a days tool; use the time calculator for hours and minutes. Legal deadlines need the exact rule that governs them, because counting rules vary by court, contract, and state. And historical dates before the Gregorian calendar was adopted in a place need historical care. Within those limits, the calculator is a reliable planning tool for everyday date arithmetic.

• Exact: calendar day counts, week counts, business day counts for a Monday to Friday week, and add or subtract results for days, weeks, months, years, and business days.
• Needs your input: holiday subtraction and weekend deadline shifts, because those rules come from your employer, court, or contract.
• Not covered: clock times, time zones, historical calendar changes, and legal interpretations of a specific deadline.

Day Counts for Routines and Streaks

Routines and streaks are counted in days, and the counting rule should be decided before the streak starts, not after it reaches a milestone. A workout streak, a reading streak, a savings streak, and a no-spend streak all use the same question: does the first day count as day one, or does the count start on the next day? Most streak trackers use the inclusive rule, where the first day is day one, so a streak that starts on January 1 reaches day 30 on January 30, not January 31. A countdown to an event uses the exclusive rule, where the event day is zero days away on the day itself. Mixing the two rules in one streak produces a celebration a day early or a day late, which feels small until it happens on a 100-day milestone.

• Workout streaks: count inclusively, and decide in advance whether a rest day breaks the streak or counts as an active recovery day.
• Reading streaks: count inclusively, and set a minimum daily amount, such as ten pages, so a token effort does not keep a streak alive.
• Savings streaks: count in days for daily saving, and in weeks for weekly saving, and keep the two counts separate.
• Habit streaks: record the start date, the rule, and the current count in one place, so the streak can be checked without argument.
• Team streaks: agree the rule in writing before the streak starts, because a disputed streak helps no one.

1. Pick the start date and write it down with the counting rule.
2. Enter the start date and today in the top half of the calculator.
3. Read the inclusive count for the streak number, and the exclusive count for elapsed time.
4. Celebrate the milestone on the date the inclusive count reaches it, and note the date for next year.

• Day 7: one week, a good first checkpoint for a new routine.
• Day 30: one month, where a routine starts to feel automatic for many people.
• Day 66: a commonly cited point where a habit feels established, though the research varies by habit and by person.
• Day 100: a round milestone, worth marking, with the inclusive rule giving the date 99 days after the start.
• Day 365: one full year, a major milestone, where the inclusive count is 365 and the exclusive span is 364 days.

Day Counts for Bills, Subscriptions, and Renewals

Bills, subscriptions, and renewals are counted in days and months, and the two units interact in ways that cause missed payments. A bill due in 30 days from October 29 is due on November 28. A subscription billed monthly on the 29th is billed on November 29, December 29, and January 29, which are 31, 30, and 31 days apart. A renewal due in one year from October 29, 2026, is due on October 29, 2027, which is 365 days later in a common year, but 366 days later if the span includes a leap day. The calculator handles each unit correctly, but the bill or contract must state which unit it uses, or the due date cannot be checked.

• Due in 30 days: add 30 calendar days, and check whether the result lands on a weekend or a holiday, when payment may process on the next business day.
• Billed monthly: add calendar months, and watch for month-end snaps when the billing day is the 29th, 30th, or 31st.
• Renewed yearly: add calendar years, and watch for the February 29 snap when the renewal date is February 29.
• Free trials: note the trial start date, the trial length in days, and the charge date, and set a reminder one day before the charge date.
• Grace periods: count the grace period from the due date, not from the statement date, and confirm whether grace days are calendar days or business days.

1. Find the start date and the unit in the bill, contract, or subscription terms.
2. Enter the start date in the bottom half of the calculator, with the number and unit from the terms.
3. Read the result date and weekday, and set a reminder one day before it.
4. Check the result against the next statement, and correct the rule if the statement date differs by one day.

Frequently Asked Questions

How many days are in 2026?

The year 2026 has 365 days. January 1 to December 31, 2026, is 364 days exclusive and 365 days inclusive. The year 2024 had 366 days because it was a leap year, and 2028 will also have 366 days.

How do I add 90 days to a date?

Enter the starting date, set the number to 90, set the unit to days, and set the direction to add. From October 29, 2026, adding 90 days gives January 27, 2027, a Wednesday. The preset button does the same thing in one tap.

How do I subtract days from a date?

Set the direction to subtract, enter the number of days, and enter the starting date. Subtracting 30 days from January 15, 2026, gives December 16, 2025. The result date and its weekday appear at once.

What is the difference between calendar days and business days?

Calendar days count every day, including weekends. Business days count Monday through Friday only. Ten calendar days from a Friday is a Monday, while ten business days from a Friday is a Friday two weeks later, because two weekends are skipped.

Does the count include the start date and the end date?

By default, the exclusive count includes neither end date as a counted day beyond the midnights between them. Tick the include box to count both end dates, which adds exactly one day. The table shows both counts so you can pick the one your purpose requires.

How many working days are in a month?

It depends on the month and the year, because months have different lengths and start on different weekdays. A 31-day month that starts on a Monday has 23 business days. A 28-day February that starts on a Monday has 20. Use the business day row in the result for the exact count in your range, then subtract weekday holidays.

What happens when I add one month to January 31?

The result snaps to the last day of February: February 28 in a common year and February 29 in a leap year. That is the calendar month rule. Adding 31 days instead would land on March 3 in a common year, which is a different operation.

Can I count days across a leap year?

Yes. The calculator includes February 29 whenever it falls inside the span. A span from February 28 to March 1 is two days in a leap year and one day in a common year, and the result reflects that exactly.

What date is 100 days from today?

Enter today as the starting date, set the number to 100, set the unit to days, and set the direction to add. From October 29, 2026, 100 days later is February 6, 2027, a Saturday. If you mean the 100th day counting today as day one, add 99 days instead.

Why does my hand count differ by one day?

The most common cause is the inclusive and exclusive difference. Hand counts often count the start date as day one and also count the end date, which is the inclusive count, while a calculator default is often the exclusive count. Check which count you used, and compare the calculator table, which shows both, before assuming either count is wrong.

Disclaimer: This calculator is for general information and planning only. It counts Gregorian calendar days and Monday to Friday business days, excluding holidays. For court, contract, or legal deadlines, check the exact counting rule that applies, because rules vary by court, contract, and state.