Free Online Tool
Date Calculator
Use it for schedules, deadlines, contracts, and date differences.
Calculation Basis
This tool calculates the difference between calendar dates or adds/subtracts days from a base date. It does not use time-of-day differences.
Inclusive Date Rules
Schedules can differ depending on whether the start date is included. Contracts and work periods should be checked against the relevant rule.
How to Use
- Choose a date mode.
- Enter dates or number of days.
- Review the result date and day difference.
Examples
- Jan 1 to Jan 31, 2026 is 30 days apart
- Find the date 100 days after a base date
What to Check in Date Differences
| Rule | Why it matters |
|---|---|
| Inclusive start date | Human-counted days and a simple date difference can differ. |
| Time zones | A date-only calculation does not replace time-zone comparison. |
| Business days and holidays | They are not included in the basic calculation. |
For contracts, deliveries, and deadlines, also check the inclusive-date rule in the relevant service or document.
Calculation and Conversion Notes
Date difference is calculated from `end date - start date`. A date after N days is calculated as `base date + N days`, and a date before N days is calculated as `base date - N days`.
What Is Not Included
Public holidays, business days, company holidays, and time-of-day differences are not included in the basic date calculation.
FAQ
Is the start date included?
Check the displayed rule. Schedules and contracts can differ depending on inclusive date handling.
Does it count holidays or business days?
No. The basic calculation uses calendar dates and does not include holidays or business days.
Do time zones affect the result?
This tool focuses on date-level calculation. Use the time zone converter for time zone comparisons.
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