- How are the weeks counted?
- The span is measured in whole calendar dates first, then divided by seven. January 1, 2026 to April 1, 2026 is 90 dates apart, and 90 divided by 7 is 12 with 6 left over, so the answer is 12 weeks, 6 days. The decimal is the same division carried out: 12.86 weeks. The start date itself isn't counted, which matches how people say "three weeks until the deadline" — you don't count today as one of them. Turn on Count the end day to include both endpoints.
- Why show both 12 weeks, 6 days and 12.86 weeks?
- They answer different questions. The whole-plus-remainder form is for planning: you can put 12 weeks on a calendar and see the 6 days hanging off the end. The decimal is for arithmetic: if something costs $340 a week, you multiply by 12.86, not by 12. Payroll, contract rates, rent proration, and gestational charts all want the decimal. Most calculators give you one or the other and make you do the conversion yourself, which is exactly the step worth removing.
- What does Count the end day do?
- It adds one day to the span before the weeks are worked out, so 90 days becomes 91 and 12 weeks, 6 days becomes a round 13 weeks. Use it when every day in the range is itself the unit being counted: the nights of a hotel stay priced per day, the days of a lease, a 30-day notice period, or a 12-week program where week one starts on the start date. Leave it off for the everyday "how many weeks until" question.
- Does daylight saving time change the answer?
- No. A lot of date tools subtract two timestamps and divide by 24 hours. On the night clocks spring forward a day is only 23 hours, so that arithmetic can land on 27.96 days and round the wrong way. This calculator counts calendar dates with integer math and never touches a clock, so March 1 to March 29, 2026 is exactly 28 days — a flat 4 weeks — in New York, in Berlin, or anywhere else, including across the March 8 change.
- What if the end date is before the start date?
- You get the same number with the word "before" after it. April 1 back to January 1 reads 12 weeks, 6 days before, the same size as the forward direction. There's no error and nothing to undo, because getting the order wrong is a typing mistake, not a question worth refusing to answer. If you meant it the other way round, swap the dates and the word disappears.
- What are two-week periods for?
- Biweekly payroll. Most US employers on a two-week cycle run 26 pay periods a year, and the quickest way to price a stretch of work is to count how many complete two-week blocks fit inside it. Ninety days holds 6 of them with 6 days spare. It's also the right unit for fortnightly billing, alternating-week custody schedules, and sprint pairs. The number is whole periods only — the remainder shows up in the day count above it.
- Which today does it use if I'm up late?
- Your own. The start date comes from your device's calendar in your time zone. At 11:30 PM on September 20 in Los Angeles it is already September 21 in UTC, and a tool that reads the UTC date will quietly prefill tomorrow and be a day out all evening. This one reads the local date, so the span you see at 11:30 PM matches the one you'd have seen at noon.
- How far back and forward does it go?
- Any two dates with years from 1000 to 9999, and leap years are handled properly. February 1 to March 1, 2028 is 29 days — 4 weeks, 1 day — because 2028 is a leap year, while the same span in 2027 is 28 days. January 1, 1900 to January 1, 2026 comes out at 6574 weeks, 3 days, or 46,021 days. A year outside that range is rejected rather than silently computed.
- Do you store the dates I pick?
- No. The whole calculation runs in your browser and nothing is sent anywhere. The only place the dates appear is the page address, as ?from=2026-01-01&to=2026-04-01, so a bookmark or a shared link reopens the same span. There's no account, no sign-up, and nothing to install. Clear the end date and it disappears from the address too.
- I need the answer in days, not weeks.
- The total days are in the secondary row here, but if days are the actual question then Days Between Dates is the page you want — it leads with the day count and adds a months-and-years breakdown this page deliberately leaves out. Keeping the two separate is the point: one page, one job. There's a link to it under the result.
