Date Calculator
Count days between two dates or add and subtract years, months, weeks, and days from any calendar date.
Days Between Two Dates
Calculate the number of calendar days from a start date to an end date, with optional inclusive counting.
Add/Subtract from Date
Add or subtract years, months, weeks, and days from a base date. Optionally count day offsets in business days only.
Formulas
Days = end − start
+ 1 if inclusive
+ 1 if inclusive
New date = base ± (y, m, w, d)
How to use this date calculator
- Days between: Pick a start and end date, optionally check “include end day” to count both boundary dates, then click Calculate.
- Add/subtract: Choose a base date, select add or subtract, enter years/months/weeks/days, and enable business days if you need weekday-only offsets for the day count.
Date calculation formulas
Calendar days = (end date − start date) in days
Inclusive days = calendar days + 1
Result = base ± years ± months ± (weeks × 7 + days)
Month and year adjustments follow calendar rules (e.g., Jan 31 + 1 month → Feb 28 or 29). Business-day mode skips Saturdays and Sundays when applying the day offset.
Example: From Jul 2, 2026 to Jul 2, 2027 is 365 calendar days (366 in a leap year if the span crosses Feb 29).
Real-world uses
- Project deadlines: Count days until a launch or delivery date.
- Contracts & leases: Find expiration dates by adding months or years to a start date.
- HR & payroll: Compute business-day due dates for invoices and approvals.
Frequently Asked Questions
It adds one day so both the start and end dates count. Jul 1 to Jul 3 inclusive is 3 days, not 2.
Business days exclude Saturdays and Sundays. When enabled, only the day offset uses weekday counting; years, months, and weeks still use calendar arithmetic.
Yes. Adding one month to Jan 31 yields Feb 28 (or Feb 29 in a leap year), matching standard calendar date roll-forward rules.