Calculate days between dates or add/subtract days from a date — free, instant, no signup required
A date calculator handles two of the most common date math problems: finding the difference between two dates (how many days, weeks, months, or years apart) and finding a new date by adding or subtracting days from a starting point. Both seem simple but get tricky fast — varying month lengths, leap years, year boundaries, and weekend handling all complicate the math when done manually. The FileTools Date Calculator handles all of this automatically using your browser's native Date object, which correctly accounts for leap years (every 4 years, except centuries not divisible by 400) and varying month lengths (28 to 31 days). All calculations happen instantly in your browser — nothing is uploaded.
Common use cases: calculating project deadlines and milestones; figuring out pregnancy due dates and trimester boundaries; planning vacations and travel itineraries; counting down to weddings, birthdays, or other special events; tracking contract durations or rental periods; calculating notice periods for resignations or evictions; figuring out warranty expiration dates; planning prescription refills; calculating exam preparation timelines; tracking how long it's been since a significant event; planning fitness or diet program durations; and any time you need to know "what date is X days from today" or "how long between these two dates."
📅 Days Between Dates: enter a start and end date to see the difference in days, weeks, months, and years. Useful for measuring elapsed time or planning durations.
➕ Add / Subtract Days: enter a start date, a number of days, and choose Add or Subtract. The result shows the new date and which day of the week it falls on. Useful for finding deadlines or anniversaries.
1 week: 7 days
2 weeks (fortnight): 14 days
30 days: ~1 month
90 days: ~3 months (one quarter)
180 days: ~6 months (half year)
365 days: 1 year (366 in leap years)
Pregnancy: ~280 days (40 weeks)
College semester: typically 105-120 days
Standard work year: ~250 business days
1. Choose a mode: Days Between Dates or Add / Subtract Days
2. For Days Between: pick a start date and an end date
3. For Add / Subtract: pick a start date, enter days, choose Add or Subtract
4. Results update instantly as you change inputs
5. The result includes day of week for Add / Subtract mode
✅ 100% free — no signup, no ads in tool, no tracking
✅ Two modes: difference between dates and add/subtract
✅ Results in days, weeks, months, and years
✅ Day of week shown for calculated dates
✅ Live updates as you type
✅ Handles leap years and varying month lengths automatically
✅ Client-side only — your dates never leave your device
✅ Works on Windows, Mac, Linux, Android, iOS — any browser
Stay in Days Between Dates mode (the default), pick the start date and end date, and the calculator instantly shows the difference in days, weeks, months, and years. The result accounts for leap years and varying month lengths automatically.
Switch to the Add / Subtract Days mode. Enter your start date, the number of days, and choose Add or Subtract from the dropdown. The calculator returns the new date along with its day of the week. Useful for finding deadlines, due dates, vacation start dates, or any future or past date.
Yes, all calendar days are counted — including weekends and public holidays. The calculator measures pure calendar duration, not business days. If you need business days only, multiply the calendar days by approximately 5/7 to estimate, or count manually for short ranges.
Days are calculated exactly using the calendar. Weeks are days divided by 7. Months are an approximate average of 30.44 days per month, and years use 365.25 days per year (accounting for leap years on average). For exact age calculations year-by-year, use the dedicated Age Calculator tool which handles month boundaries precisely.
Yes. The calculator uses JavaScript's native Date object, which correctly handles leap years (every 4 years, except centuries not divisible by 400) and varying month lengths automatically. Days between dates always reflect actual calendar days lived.
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