Date Calculator 2026 — Difference & Add/Subtract Days
Find the exact number of years, months, weeks and days between two dates, or add and subtract time from any date — instantly, accounting for leap years and varying month lengths.
Date Difference or Add/Subtract?
Use “Date Difference” to find how much time falls between two dates — for age, deadlines, or anniversaries. Use “Add/Subtract Days” when you have one date and need to find another that’s a set number of days, weeks, months or years away.
Date Difference Calculator
Enter a start and end date to find the time between them
Defaults to today’s date — change it to any date you like.
Adds 1 day to the total — useful for counting event or booking days rather than elapsed time.
Date Difference Result
Years, months, days, and total duration
Pick a start and end date, then click Calculate Date Difference to see the full breakdown.
Add/Subtract Days Calculator
Enter a date and a duration to find the resulting date
Fill in any combination — leave the rest at 0.
Add/Subtract Result
Resulting date and day of the week
Pick a starting date and duration, then click Calculate New Date to see the result.
Handy Date Conversions
Quick reference figures used in everyday date math — useful for double-checking calculator results or doing rough estimates by hand.
| Unit | Equals | Notes |
|---|---|---|
| 1 Week | 7 days | Always fixed |
| 1 Month (avg) | ~30.44 days | Ranges from 28 to 31 days |
| 1 Year (common) | 365 days | 52 weeks + 1 day |
| 1 Leap Year | 366 days | Occurs roughly every 4 years |
| 1 Decade | 3,653 days (avg) | Includes ~2–3 leap years |
| Leap Year Rule | Divisible by 4 | Except centuries not divisible by 400 |
Date Calculator FAQ
Everything you need to know before working out dates and durations in 2026.
Convert both dates to a common reference point (such as days since a fixed epoch) and subtract the earlier date from the later one. This calculator does that automatically and also breaks the result down into full years, months and remaining days, plus the total in weeks and days.
By default the calculator counts the number of days elapsed between the start and end date, not the number of calendar days touched. If you need an inclusive count (counting both the first and last day), simply add 1 day to the result shown, or tick the inclusive option provided.
Enter your starting date, choose whether to add or subtract, then enter the number of days, weeks, months or years. The calculator adjusts the calendar correctly, including leap years and varying month lengths, and returns the resulting date along with its day of the week.
Yes. Both the date difference and add/subtract calculators use standard calendar arithmetic, which automatically accounts for leap years (including the extra day in February) so that every result reflects the real Gregorian calendar.
Yes. Enter your date of birth as the start date and today’s date as the end date in the Date Difference tab, and the calculator will show your exact age in years, months and days, along with the total number of days and weeks you have been alive.
Calendar years and months are not a fixed number of days — months range from 28 to 31 days and years can be 365 or 366 days. The calculator counts whole calendar years and months first, then shows the leftover days, which is more accurate than dividing the total day count by a flat average.