Date Calculator
Compute the exact time between two dates or add/subtract days, weeks, months, or years. Weekdays-only supported.
Your dates
Final result
Results interpretation
- Calendar vs. totals: We show an exact calendar breakdown (years, months, days) and totals in days/weeks.
- Weekdays-only: Counts Monday–Friday; holidays are not excluded.
- Who it’s for: Project plans, HR/eligibility windows, event timelines, and legal deadlines.
How this calculator works
Differences are computed from whole calendar days between dates. The calendar breakdown borrows days and months when needed, mirroring how people express durations.
Show math & assumptions
- Let
AandBbe dates at local noon to avoid DST issues; reorder soA ≤ B. - Total days:
Δ = ⌊(B − A)/86400000⌋(+1 if inclusive). - Weeks:
⌊Δ/7⌋, remainder:Δ mod 7. - Weekdays: full weeks × 5 + weekdays in the remainder starting from
A. - Add/subtract months/years: clamp to last day of target month if needed.
FAQ
Do you include the end date?
Toggle “Include end date” to count it. Many deadline calculations are inclusive.
What does “weekdays only” mean?
We count Monday–Friday. Federal or local holidays are not excluded.
Why don’t you count hours/minutes?
This is a date-only tool. For time-of-day precision, use a datetime calculator.
How do you handle month lengths when adding months?
We clamp to the last valid day—e.g., Jan 31 + 1 month → Feb 29 (leap year) or Feb 28 (non-leap).
Can I subtract business days?
Use “Skip weekends” with unit = days, then choose Subtract.
Why do other sites show a different total?
They may count inclusively by default, use time-of-day, or a different weekend/holiday policy.
Use cases & examples
- Deadline planning: Start 2025-03-01, add 45 weekdays → skip weekends to find the due date.
- Event countdown: Between 2025-08-01 and 2026-05-20 with “Include end” to get inclusive days.
- Project phases: Add 6 months to contract signature; clamping handles month ends safely.
What this Date Calculator does
Date calculator tools answer two core questions fast: How many days are between two dates? and What date is a certain number of days, weeks, months, or years from a starting point? This page is built for clarity and speed—pick your mode, enter dates and options, and see both a step-by-step explanation and a clean final answer.
Finding the difference between two dates
Use the Between dates mode to measure a span. We compute the exact number of calendar days, optional inclusive counting, an easy weeks+days breakdown, and a calendar-accurate years–months–days view. Choose Weekdays only to ignore Saturdays and Sundays—useful for workback schedules and delivery SLAs.
Adding or subtracting time
Switch to Add / Subtract to project forward or backward. Days and weeks use straight calendar arithmetic, while months and years clamp safely to the last day of the target month to avoid invalid dates. For day-level work calendars, toggle Skip weekends (for “days” only) to walk past Saturdays and Sundays automatically.
Why inclusive counting matters
Legal and academic contexts often include the end date. For example, a “90-day inclusive” window starting May 1 ends on July 29, not July 30. Use the checkbox to match your policy and avoid off-by-one mistakes.
Common pitfalls
- Assuming all months have 30 days—harmful when adding months from month-end dates.
- Forgetting to specify inclusive/exclusive rules on deadlines.
- Mixing in time-of-day or time zones for a date-only calculation and creating DST artifacts.
Limitations
This tool works with dates, not times, and does not exclude holidays. If you need holiday calendars or time-zone aware math, use a specialized scheduling system.
Practical examples
Example 1: Start 2025-01-15, add 2 months → 2025-03-15. From Jan 31, adding one month clamps to Feb 28/29 depending on leap year.
Example 2: Between 2025-06-01 and 2025-06-30 inclusive → 30 days; exclusive → 29 days.
Example 3: Base 2025-08-01, add 10 weekdays → skips two weekends to land on a Monday.