How many weeks between two dates
Whole weeks and the days left over, plus the ISO week number each date falls in — the two things a "how many weeks" question usually needs.
Weeks between two dates
Whole weeks, or weeks and days?
Between 1 March and 1 May there are 61 days: 8 whole weeks and 5 days. Saying "about 9 weeks" rounds up, "8 weeks" rounds down, and for a due date, a course length or a notice period the leftover days are usually the part that matters. The result gives both.
Weeks and ISO week numbers are different things
The number of weeks between two dates is arithmetic. An ISO week number is a label: weeks run Monday to Sunday, and week 1 is the one holding the first Thursday of January. Two dates 8 weeks apart are always 8 ISO week numbers apart, but the numbers restart each year, so counting across New Year needs the dates, not the labels.
Calendars printed here can show the ISO week number down the margin, which makes a plan built on week numbers legible at a glance.
Pregnancy, notice periods and sprints
The common uses of a week count share a habit: they start from a known date and run in whole weeks. Set the start date, then move the end date until the whole-week figure reads what you need — the exact calendar date appears as you go.
Questions
How many weeks are in a year?
52 weeks and 1 day in a common year, 52 weeks and 2 days in a leap year. In ISO week numbering most years have 52 weeks and some have 53 — 2026 has 53.
Why does the result show days as well as weeks?
Because two dates are rarely a whole number of weeks apart. Rounding to whole weeks can move a deadline by up to six days, so the leftover days are shown rather than hidden.