Days Since Calculator: How Many Days Since (or Until) a Date?

How do you calculate how many days since a date?

Subtract the start date from today's date, counting calendar days. From January 1 to November 1, 2026, that's 304 days. The start day itself is not counted, which is how most calculators and spreadsheets count. It also makes November 1 day 305 of the year: the days since January 1 are always the day of the year minus one.

By hand, it takes four steps:

1. Finish the first month. January has 31 days, so after January 1 there are 30 days left.
2. Add the full months in between. February to October 2026 is 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 = 273 days.
3. Add the days into the last month. November 1 adds 1 day.
4. Check for February 29. 2026 is not a leap year, so nothing to add. Total: 30 + 273 + 1 = 304 days.

In Excel or Google Sheets it's one formula. Put your date in cell A2 and type =TODAY()-A2 (format the cell as a number), or =DAYS(TODAY(),A2). For whole years, use =DATEDIF(A2,TODAY(),"Y"), and for the months left over, "YM". Skip the "MD" unit: Microsoft's own DATEDIF help page says it doesn't recommend it, because it can return a negative number, a zero or a wrong result.

Does the start day count? "Days since" vs "Day 1"

"Days since" counts the days that have passed, so the start day is day zero. "Day 1" counting includes the start day, so the Day number is always one higher than the days since. Start a habit on a Monday, and on Tuesday it's been 1 day since you started, and it's also Day 2.

For elapsed time, like how long ago something happened, use days since. For things you show up for, like a habit, a challenge or a streak, most people count the first day as Day 1: if you did it today, today counts.

That one-day gap is why calculators disagree. Most leave the start day out; some offer an "include end date" option, which adds one. Subtracting two dates in a spreadsheet leaves one out, while Excel's NETWORKDAYS function counts the workdays from the start date through the end date, both included. So from Monday, November 2 to Monday, November 9, 2026, this calculator counts 5 weekdays and NETWORKDAYS counts 6. Microsoft's own example, October 1, 2012 to March 1, 2013, returns 110 workdays; the same dates here give 109, or 110 with Day 1 counting.

Our suggestion: pick one rule and keep it. The calculator's "Count the start day as Day 1" switch shows both numbers.

Days since milestones: 100, 365 and 1,000 days

A milestone date is your start date plus the number of days. 100 days after November 1, 2026 is Tuesday, February 9, 2027, and 100 days before it was Friday, July 24, 2026. With Day 1 counting, every milestone falls one day earlier, because the start day already counts as Day 1.

The table counts from November 1, 2026. For any other date, use the "Add or subtract" mode, or enter your start date and read your milestones under the result.

Round numbers give a long count something to aim for: Day 304 feels like any other day, Day 365 is a date for your calendar. The calculator names your next one and can save it as a calendar event.

How many days until a date?

Count the other way around: the future date minus today. From November 1, 2026, there are 54 days until December 25, 2026. That's 7 weeks and 5 days, or 1 month and 24 days. Pick "Days until" in the calculator, or type a future date under "Days since" and it switches over for you.

A countdown and a count-up work well together. Count down to the day something starts, like a race, a trip from your bucket list or one of the easier 75 Hard alternatives. On the day itself, switch to "Days since", turn on Day 1 counting and let the number grow.

Leap years, time zones and months: why the count can surprise you

Three things make date math feel off: leap years add a day, daylight saving time makes one day 23 or 25 hours long, and months run from 28 to 31 days. Count whole calendar days, the way this calculator does, and only the leap day changes the number.

Leap years

The Gregorian calendar has a leap year every 4 years, except century years that don't divide by 400: 2000 was a leap year, 1900 was not. So February 28 to March 1 is 2 days in 2024 and 1 day in 2023. Britain and its American colonies switched to this calendar in 1752, when Wednesday, September 2 was followed by Thursday, September 14. For earlier dates, the calculator extends the Gregorian calendar backward and adds a note.

Daylight saving time and time zones

When US clocks jump forward in spring, that Sunday is 23 hours long; when they fall back, it's 25. Each still counts as one day, because the calculator counts dates, not hours. "Today" is your device's local date, so someone in another time zone can see one day more or less until midnight.

Why "months since" is never exact

Months aren't a fixed length, so "months since" is a convention, not a measurement. When a month is too short for your day, we use its last day: January 31 plus one month is February 28, so January 31 to March 1, 2026 is "1 month, 1 day". When it matters, trust the day count.

How this calculator counts

This calculator turns each date into a day number, with no time of day, and subtracts. It never measures the time between two clock readings, so daylight saving time can't shift the count by a day. Everything happens in your browser.

• Days since: end date minus start date. Day 1 counting adds one.
• Weekdays: Monday to Friday from the start date up to the end date. Day 1 counting includes the end date. Holidays are not taken out.
• Hours: days × 24 as an estimate; exact only when you add a time of day.
• Anniversaries: the same month and day each year. A February 29 start has its anniversary on February 28 in other years.

Your link carries the dates and switches, so it recounts whenever you open it. An optional label rides after the #, the part a browser never sends to a server.

What people track with a days since counter

Most counters mark a stop, a start or a last time: the day you quit something, the day you began something, or the last time something happened. Behind nearly every one is a date that means something to you, and a number you check because it shows how far you have come.

• Since you quit something: smoking, sugar, energy drinks or late-night scrolling. If the scrolling is the one, the screen time calculator shows what those hours add up to. Our list of bad habits and what to replace each one with helps you decide what fills the gap.
• Since you started something: a job, a relationship or a habit from our list of good habits to build.
• Since the last time it happened: the workplace "days since last incident" board, or the last time you called your parents.
• Since a big moment: a move, a wedding, or January 1, if you're keeping one of your New Year's resolutions.

"Days without" counts an absence (no cigarettes); "days of" counts something you do every day (a walk). Both work as a streak, as long as you say each morning what counts as a day.

Calculator or day counter app: which do you need?

A calculator gives you one exact answer right now. A day counter app keeps a number on your phone that grows by itself. A habit app with streaks counts only the days you actually show up. Pick by whether you want to know a number, watch it, or earn it.

• Use this calculator if you want an answer in seconds or a link to bookmark and share. No install, no account.
• Use a day counter app if you want the number on your home screen and mostly count time passing, like days until a trip.
• Use a habit app if the number should depend on you: a counter keeps going on the days you slip, a streak only grows when you do the thing.

"200 days since I started running" is true even if you ran twice. "Day 200 of my running streak" means you showed up. Missed a day? Our Atomic Habits cheat sheet has the rule for that: never miss twice.

Turn your days since into a daily streak

A date tells you how long it's been; a streak tells you how often you showed up. If your date is the day you started a habit, the next step is to earn each day that follows: do the habit, mark the day, and let the count grow only when you do.

Greatr is one way to do that. You put the habit in your morning or evening routine, run it each day, and Greatr counts every day you show up, with medals like the 30 Day Streak along the way. Otto, your guide in the app, keeps count in his notebook:

Yesterday is already in my notebook. Today, we add one more day.

How long until it sticks? In a 2010 study by Phillippa Lally and colleagues, a new daily habit took a median of 66 days to feel automatic among participants whose data fit their model, with estimates from 18 to 254 days. That's a median, not a promise. Started on January 1, 2026? Day 66 was March 7, 2026. Your next step: enter your start date above, turn on Day 1 counting, and bookmark the link.