Add Days Calculator - Count or Add Days, Both Ways

An add days calculator is a calendar-day tool that counts the number of days between any two user-picked dates, or adds (or subtracts) any chosen number of days to a start date, with an optional Include end date toggle. It also reports the weekday, full weeks, approximate months, weekend days, and business days inside the same range.

• • Counting days between two events: Pick a from date and a to date and the calculator returns the day count plus weekday, week, weekend, and business-day totals. Useful for the gap between a move-in date and a move-out date, or a contract start and end.
• • Adding N days to a deadline: Need to know what date is 30, 60, 90, or 180 days from today or from a project start? Switch to add/subtract mode and the calculator walks the calendar one day at a time so the resulting date is correct across month boundaries and leap years.
• • Subtracting days to find a start date: If you have a fixed end date and need to know when to start a 30-day notice period, switch to subtract mode. The calculator returns the start date that lands N days before the target.
• • Estimating business days and weekend days: The result panel reports Mondays-through-Fridays and Saturdays-plus-Sundays inside the range, which is useful for staffing, payroll, school terms, and any plan that ignores weekends.

The math is simple date arithmetic, but month lengths vary and February 29 only shows up every four years. This tool follows the same convention as the Omni add days page: it counts every calendar day by default and lets the user decide whether the end date is included.

If both dates are already fixed and you only need the gap between them, the days between dates calculator returns the day count directly.

It uses standard calendar arithmetic: it reads the mode, the from and to dates, the include-end-date toggle, and (in add/subtract mode) the N-day offset and direction, then iterates the inclusive day range to derive the weekday, week count, month count, weekend day count, and business day count.

• fromDate: The first date in the range, or the date the N-day offset is applied to in add/subtract mode.
• toDate: The end date of the range in range mode. In add/subtract mode it is set automatically to the resulting date.
• includeEndDate: Off (default) excludes the end date from the day count. On adds one extra day and is used when counting nights, contract days, or any inclusive span.
• mode: Range mode counts days between two dates. Add/subtract mode applies an N-day offset to the from date.
• numberOfDays: The N-day offset applied in add/subtract mode. Default 30, valid 1 to 10,000.

According to Time and Date, a leap year contains 366 days with the extra day inserted at the end of February, while a common year contains 365 days, which is why 1 Jan to 31 Dec 2024 returns 366 days with the end date included and 365 days with it excluded

According to Omni Calculator, the standard add days counter measures the number of days between two user-picked dates, excludes the end date by default, supports a Working time option that returns 261 business days in 2024, and a Custom time option that lets the user include or exclude specific weekdays

If your plan needs a 90-day review cycle instead of an arbitrary N-day offset, the 90 day calculator returns a 90-day result with the same weekday, week, weekend, and business-day breakdowns.

Four ideas explain every value the panel shows:

These definitions matter when the result is shared. A 30-day plan almost always means calendar days, but a 30-day payroll cycle almost always means business days, so match the convention to the audience. The 104-weekend-day figure for 2024 is the easiest sanity check.

When you need to combine a from-to range with an add/subtract offset in a single screen, the date calculator covers the same arithmetic.

Five short steps are enough to get a trustworthy day count.

1. 1 Choose the mode: Use range mode when you have a from and to date. Use add/subtract mode when you have a start date and want to know what date lands N days later (or earlier).
2. 2 Enter the dates: In range mode, pick the from and to dates. In add/subtract mode, pick the start date (the to date is set to the resulting date).
3. 3 Decide whether to include the end date: Leave the toggle off for the standard add days convention. Turn it on for an inclusive count, such as nights stayed or contract days.
4. 4 Set the N-day offset in add/subtract mode: Leave it at 30 for a default monthly count, or change it to any whole number from 1 to 10,000. Pick add or subtract to move forward or backward in time.
5. 5 Read the result and the breakdowns: The result panel shows the day count, the resulting date, its weekday, the full-week count, the approximate months, the weekend days, and the business days.

Practical example: a 30-day notice period that starts on Sunday, 14 June 2026 with the end date excluded returns Tuesday, 14 July 2026 with 4.3 full weeks, 1.0 approximate months, 8 weekend days, and 22 business days.

A purpose-built day counter saves time and removes calendar-counting errors.

• • Removes leap-year and month-length errors: The calculator handles the 28-day February, the 29-day leap February, and the 30 vs. 31-day months for you.
• • Works in both modes without switching tools: Range mode covers a from-to day count, and add/subtract mode covers an N-day offset.
• • Surfaces the weekday early: The weekday of the resulting date is shown next to the date so you can plan around workdays and avoid landing a milestone on a weekend.
• • Reports business days alongside weekend days: The business-day count is the right number for payroll and school terms, and the weekend-day count is the right number for trip planning.
• • Pairs with custom N-day offsets: The N-day offset field accepts any whole number from 1 to 10,000, so the same calculator covers 7-, 14-, 30-, 60-, 90-, 120-, 180-, and 365-day plans.

If you already have two fixed dates and just need the gap between them, the days-between-dates tool is a faster fit; if you need a live timer toward a single deadline, the date countdown tool is a better fit.

If your plan needs a 30-day monthly cycle, the 30 day calculator counts exactly 30 calendar days with the same breakdowns this calculator uses.

Three variables determine what the result looks like, and two limitations tell you when to double-check the answer.

• • The result is a calendar-day count. It does not subtract public holidays, school breaks, or company shutdowns, so any business-day interpretation that ignores public holidays needs a separate tool.
• • The approximate months figure uses a 30.42-day average and is meant for at-a-glance planning. For exact calendar-month arithmetic, anchor the start and end dates to a calendar.

The weekend-day count is the easiest signal to read on the result panel: a count of 8 for a 30-day range means the 2 extra days fell on weekdays, and a count of 9 means at least one extra day fell on a Sunday.

According to Time and Date, a 365-day year divides into 12 equal months of about 30.4167 days, which is the divisor this calculator uses for the approximate month count and the quarterly baseline of about 91.25 days

For a live timer toward a single deadline, the date countdown calculator shows the days, hours, minutes, and seconds remaining.