One rule decides every date on this page: Day 1 is the start date itself. So a 75-day run spans 74 nights, and the last day is start + 74 — not start + 75. Reverse the calculator and the same rule runs backwards: to finish on a chosen date, Day 1 is that date minus (length − 1). Getting this wrong by one is the single most common mistake in a challenge calendar, and it is why the page prints the weekday of Day 1 as well as the date.
The statistics beside the result are direct. Weeks and days are the length divided by seven with the remainder shown, so 75 days is 10w 5d. Months divide by 30.44, the average length of a calendar month across a common year — 365.25 ÷ 12 — because dividing by 30 overstates a long run. Weekend days are counted by walking every day of the run and testing its weekday, not estimated from the length, so a run that starts on a Saturday and one that starts on a Tuesday give different answers, as they should.
The band underneath is drawn against a fixed 100-day scale rather than being stretched to fill the width. That is deliberate: a scaled drawing makes a 30-day run and a 100-day run the same picture, which is the one thing a length visualiser must never do. A custom run longer than 100 days stretches the scale instead of overflowing, and the caption says which scale is in force.
Six marks land on the band: Day 1, Day 21, Day 30, halfway, three quarters and the last day, with halfway and three quarters rounded to whole days. Marks that fall outside the run, or on a day another mark already holds, are dropped rather than stacked — a 30-day run therefore shows five marks, not six, because Day 30 and the last day are the same day.
Unbroken counts days. It does not measure anything about your body, and nothing above is medical,
nutritional or fitness advice. Where a number here is our own judgement rather than a published figure,
the note says so and cites nothing.
Method last checked 21 August 2026.
