How do you count difference in years, months and days?

We compute completed calendar years, then remaining months, then remaining days by borrowing from months when needed (standard calendar method).

Does the business day counter handle holidays?

Yes — you can specify a comma-separated list of holiday dates (YYYY-MM-DD) to exclude them from business day counts.

How are months handled when adding months to end-of-month dates?

If the target month has fewer days than the source day, the result becomes the last day of the target month (e.g., Jan 31 + 1 month → Feb 28/29).

Date Calculator

Date tools — difference, add/subtract, age & weekday

Operation

Start date

End date

Include end date

Inclusive counts both start and end; exclusive counts days between.

Custom holidays

Optional: list dates to treat as non-working days (format YYYY-MM-DD).

Days to add/subtract

Use negative numbers to subtract (e.g., -7).

Months to add/subtract

Handles end-of-month: adding 1 month to Jan 31 → Feb 28/29.

Display precision

Precision used for numeric outputs where relevant. Date outputs use ISO (YYYY-MM-DD) and weekday names.

Results

Choose an operation, enter dates, then press Calculate.

Date calculator concepts & examples

Short practical explanations so you can interpret outputs and apply them to planning, schedules, legal deadlines and reports.

Exact difference (years, months, days)

We calculate the exact calendar difference by counting completed years, then remaining months, then remaining days. Example: from 2023-08-15 to 2025-12-18 → 2 years, 4 months, 3 days.

Total days vs weeks

Total days is the simple count of days between two dates. Weeks = total days ÷ 7 (with remainder). Both inclusive and exclusive counting options are supported.

Business days

Business days exclude Saturdays and Sundays. You may also add custom holidays (specific dates) to be treated as non-working days when counting business days.

Adding months — end-of-month rules

When adding months, this tool preserves the day number when possible. If the destination month is shorter, the result is the last day of that month (e.g., adding one month to Jan 31 → Feb 28 on non-leap years, Feb 29 on leap years).

Leap years

Leap years have 29 days in February (years divisible by 4, except centuries not divisible by 400). The calculator handles leap-year rules correctly when computing differences and adding months.

Age calculation

Age is presented as exact years, months and days from date of birth to today (or to a chosen reference date), accounting for calendar variability and leap years.