Date Calculator
Two tools in one: the exact gap between two dates, and any date plus or minus days, weeks, months or years.
Date arithmetic hides everywhere: contract deadlines ("90 days from signing"), visa windows, project timelines, pregnancy milestones, return policies, or just settling how many days are left until a trip. Counting on a wall calendar invites off-by-one mistakes; this calculator does both directions of the job exactly — the gap between two dates, and a date shifted by any amount.
The difference panel shows the gap four ways, because different situations count differently: total days (the unambiguous number), weeks plus days (project planning), calendar months plus days (leases and billing), and weekdays only — the Monday-to-Friday count that business deadlines usually mean. The add/subtract panel answers "what date is 90 days from today?" and names the weekday, since a deadline that lands on a Sunday is worth knowing about in advance. Leap years and month lengths are handled by real calendar math throughout. For ages specifically — years, months and days from a birth date — the age calculator adds birthday-aware details.
How to use the Date Calculator
- For a date difference: pick the From and To dates and read the gap as days, weeks, calendar months and weekdays.
- For date shifting: pick a base date, choose Add or Subtract, enter an amount, and pick days, weeks, months or years.
- The shifted result names the weekday and shows how far it is from today.
- Swap the dates freely — a reversed range simply shows as negative days.
Frequently asked questions
Is the end date included in the count?
No — the count is exclusive of the end date, matching how "days between" is usually meant: Monday to Friday of the same week is 4 days. If your contract counts inclusively ("including both days"), add 1 to the result.
What counts as a weekday in the weekday count?
Monday through Friday. Public holidays aren't excluded — they vary by country and industry — so for "business days" in the legal sense, subtract the holidays that apply to you from the weekday figure.
How does adding a month handle the 31st?
Standard calendar behavior: adding one month to January 31 lands on March 2 or 3 (JavaScript rolls the overflow forward), because February has no 31st. For end-of-month schedules like billing, anchor to the 1st and subtract a day instead.
Does it handle leap years?
Yes — all math uses real calendar dates, so February 29 exists in leap years and the day counts across them are exact. That's why "1 year" from a date is sometimes 365 days and sometimes 366.
Can I calculate a deadline like "45 business days from today"?
Directly, no — the add panel works in calendar units. A quick approximation: 45 business days ≈ 63 calendar days (multiply by 7/5), then verify the weekday count with the difference panel and nudge by a day or two.