Week calculator from date
Pick a from date and a to date to see how many weeks are between them. The from date starts as today, so you can count the weeks until a date straight away.
- Weeks
- 12 weeks
From September 30, 2026 to December 23, 2026 is 12 weeks.
- In weeks
- 12
- Days
- 84
- In years, months, and days
- 2 months, 23 days
Answer for the example date Wednesday, September 30, 2026. It changes to today's date when the page loads.
Weeks: 12 weeks. From September 30, 2026 to December 23, 2026 is 12 weeks.
Where are the dates on the calendar?
How to calculate
Counts the weeks from one date to another: whole weeks and days, the same span as a decimal number of weeks, and in months and days.
Example with the default inputs (From date September 30, 2026, To date December 23, 2026) on the example date Wednesday, September 30, 2026: From September 30, 2026 to December 23, 2026 is 12 weeks.
Method: days = to date − from date; weeks = days ÷ 7 rounded down, with days − 7 × weeks days left
- Dates are whole calendar days in the Gregorian calendar, with no time of day.
- The from date is not counted and the to date is: from a Monday to the next Monday is 1 week.
- The from date is today unless you change it; the page reads today’s date from your device when it loads.
- A from date after the to date has no answer.
Worked examples
Each example is checked against the calculator on every build.
- From date 2026-09-30, To date 2026-12-25 gives Weeks 12 weeks, 2 days, In weeks 12.285714, Days 86, In years, months, and days 2 months, 25 days.Source: Julian Day numbers (Meeus, Astronomical Algorithms, 1991, chapter 7): JD 2461399.5 − JD 2461313.5 = 86 days
- From date 2026-01-01, To date 2026-12-31 gives Weeks 52 weeks, In weeks 52, Days 364.Source: Gregorian calendar (ISO 8601): a common year has 365 days, 52 weeks and 1 day
- From date 2024-02-01, To date 2024-03-01 gives Weeks 4 weeks, 1 day, In weeks 4.142857, Days 29.Source: Gregorian leap-year rule (ISO 8601)
How it works
Dates are whole calendar days in the Gregorian calendar, with no time of day. Dates from January 1, 1600 to December 31, 2400 are accepted, and the from date must be on or before the to date; otherwise there is no answer.
- Days = to date − from date, in whole days. The from date is not counted and the to date is.
- Weeks = days ÷ 7, rounded down, and the days left = days − 7 × weeks (0 to 6).
- In weeks = days ÷ 7 as a decimal, shown to 2 decimal places.
- In years, months, and days: from the from date, the most whole years, then the most whole months, then the days left, as in an age. A day that a month does not have moves to the month’s last day.
The from date starts as today and the to date as 12 weeks after today. The page was built on one day and may be opened on another: the built page shows the dates of its build day, and your browser replaces them with yours as soon as the page loads.
Worked examples by hand
September 30, 2026 to December 25, 2026. October has 31 days and November 30, so September 30 to December 25 is 31 + 30 + 25 = 86 days. 86 = 12 × 7 + 2: 12 weeks and 2 days, or 86 ÷ 7 = 12.29 weeks. September 30 plus 2 months is November 30, and 25 more days is December 25: 2 months and 25 days.
January 1, 2026 to December 31, 2026. 2026 is a common year of 365 days, so the count is 364 days = 52 weeks exactly.
February 1, 2024 to March 1, 2024. February 2024 has 29 days, so the count is 29 days = 4 weeks and 1 day, or 4.14 weeks.
Other questions people ask
How do I count the weeks between two dates?
Count the days from the first date to the second, then divide by 7. The whole number is the weeks and the remainder is the days left. From September 30 to December 25, 2026 is 86 days, and 86 = 12 × 7 + 2, so 12 weeks and 2 days.
How many weeks are there until a date?
Leave the from date as today and enter the date as the to date. The page reads today’s date from your device when it loads, so the count is right on the day you open it.
What does the decimal number of weeks mean?
It is the days divided by 7, so 12 weeks and 2 days is 86 ÷ 7 = 12.29 weeks. Use it when a form asks for weeks with a decimal point.
Is the first day counted?
No. The count is the days from the from date up to the to date, so from a Monday to the next Monday is 7 days, which is 1 week. The same date twice is 0 weeks.
How many weeks are in a year?
A common year has 365 days, which is 52 weeks and 1 day; a leap year has 366 days, 52 weeks and 2 days. From January 1 to December 31 of a common year is 364 days, exactly 52 weeks.
Can the to date be before the from date?
No. If the to date is before the from date there is no answer; swap the two dates.