What is 21 days from today?
21 days from today is
If today is day 1 of a 21-day challenge, the last day is .
21 days = 3 weeks, about 0.7 months.
Another length? Open the full end date calculator.
Opens the free contract builder with your start date and 21 days filled in. No email, no sign-up.
Day 0 or day 1? The big date counts today as day 0, the way date calculators do, so it is exactly 21 days after today. A challenge counts its first day as day 1, so a 21-day challenge that starts today ends one day earlier, on the last day shown under the date.
If you start on one of the next seven days
Each row is a 21-day challenge with that date as day 1, and the date exactly 21 days after it.
| Start (day 1) | Last day (day 21) | 21 days later |
|---|---|---|
| Turn on JavaScript to see the dates for the next seven start days. The last day of the challenge is always 20 days after the start, and the date 21 days later is the day after that. | ||
21 days in weeks, months and hours
| Weeks | 3 weeks |
|---|---|
| Months | About 0.7 months, using an average month of 30.4 days |
| Years | 0.06 of a year |
| Hours | 504 |
| Minutes | 30,240 |
21 days is exactly 3 weeks, so 21 days from today always falls on the same day of the week as today.
On the calendar, the number of whole months depends on the start date, because months have 28 to 31 days.
Where the 21-day habit idea comes from
The claim that it takes 21 days to form a habit is usually traced to Maxwell Maltz, a plastic surgeon who wrote Psycho-Cybernetics in 1960. He noticed that patients seemed to need a minimum of about 21 days to get used to a change, such as a new face after surgery, and suggested that changes to our self-image take a similar time. Over the years "a minimum of about 21 days" was retold as "21 days to form a habit".
Later research does not support a fixed number. In a 2010 study at University College London, Phillippa Lally and colleagues followed volunteers who repeated a new daily behaviour. The median time for it to feel automatic was 66 days, and individual results ranged from 18 to 254 days. So treat 21 days as a rule of thumb: long enough to learn what a habit costs you and whether you want to keep it, short enough to commit to without a long run-up. If it goes well, a 66-day or 90-day run is a natural next step.
Good uses for 21 days
- A trial run. Three weeks of a habit you are thinking of keeping for months, before you commit to the long version.
- A gratitude or journaling streak. The gratitude challenge plan works for 21 days as well as 30.
- A reset before an event. Three weeks without added sugar (see the no sugar challenge) or alcohol that ends before a holiday, trip or race.
- Three tidy weeks. 21 days is exactly 3 weeks, so a challenge that starts on a Monday ends on a Sunday, and every week has the same shape.
Questions
What day of the week is 21 days from today?
The same day of the week as today. 21 days is exactly 3 weeks, so if today is a Wednesday, 21 days from today is also a Wednesday.
How many weeks and months is 21 days?
21 days is exactly 3 weeks, or about 0.7 months, since an average month is about 30.4 days. It is 504 hours.
What is 21 days from tomorrow?
One day later than 21 days from today, and the same day of the week as tomorrow. Tap From tomorrow in the box at the top of the page to see the date.
Does it take 21 days to form a habit?
Not reliably. The 21-day figure goes back to Maxwell Maltz's 1960 observation that people needed a minimum of about 21 days to adjust to a change. A 2010 University College London study by Lally and colleagues found a median of 66 days for a new daily behaviour to feel automatic, with a range of 18 to 254 days. Twenty-one days is a useful trial, not a deadline.
If I start a 21-day challenge today, when does it end?
On day 21, which is 20 days after today and one day before the date 21 days from today. A challenge that starts on a Monday ends on a Sunday.
Turn the date into a plan
Make it a 21-day challenge opens the contract builder with your start date and length filled in. Write your rules, sign a one-page contract, print a calendar with a box for each of the 21 days, and check in each evening on the daily tracker. It is free, needs no account and keeps your data in your browser.