Weeks Between Dates
Count full weeks and extra days between any two dates.
Written by Golam Rabbani, Founder & Lead Engineer
How to use this weeks between dates
- Pick a start date.
- Pick an end date (in either order).
- Press "Calculate weeks".
- Read full weeks + extra days, decimal weeks, and total days.
- Use Reset to clear or Copy to share the answer.
About this weeks between dates
Weeks-between-dates is a simple, accurate count of the 7-day blocks separating two calendar dates. The tool converts both dates to UTC midnight, takes the difference in milliseconds, and divides by the number of milliseconds in a day to get a total-days figure. It then divides total days by 7 for full weeks, takes the remainder for extra days, and divides total days by 7 to two decimals for the decimal-weeks figure.
Because the math runs in UTC, there is no timezone shift to worry about: 2026-01-01 and 2026-03-01 always count as 59 days, regardless of where you are. The direction field tells you whether the second date is forward, backward, or the same as the first — the magnitudes match either way.
Worked example: enter start 2026-01-01 and end 2026-03-15. The tool reports 10 weeks and 3 days, decimal weeks 10.43, total days 73, direction forward. If you flip the order it shows the same numbers with direction backward, so you can compare ranges without worrying which is which.
Useful for pregnancy week counting, training cycles, project sprints, or any planning that thinks in weeks.
FAQ
- Are partial weeks counted?
- Yes — they appear as "extra days" alongside the full weeks, and the decimal weeks field rolls them into a fraction.
- Does it matter which date I put first?
- No. The tool sorts the dates internally and tells you the direction so you know whether the end was forward or backward of the start.
- Will timezone affect the answer?
- No. Both dates are compared as calendar dates at UTC midnight, so the same input always gives the same answer.
- How is this different from ISO week numbering?
- ISO week numbers label a week with a single integer per year. This tool counts the duration between two dates in weeks — different question, different output.