How Many Days Between Two Dates? Count Workdays, Weekends and Exact Years-Months-Days

Keywords: date calculator, days between two dates, workday calculator, add days to a date, date difference, day counter

How many days until the move-in date? When does a 90-day probation end? What is the date 100 days from today? These questions look trivial, yet hand counting is usually off by one. The causes are almost always the same three: inclusive or exclusive counting, uneven month lengths, and weekends.

1. Inclusive vs. exclusive: is the 1st to the 10th nine days or ten?

• Exclusive (the default for date differences): 10th minus 1st = 9 days.
• Inclusive (both ends count): 1st to 10th = 10 days. This is how people count hotel nights, leave days or streaks.

Decide which one you need before you calculate.

2. Do not approximate months as 30 days

"2 years, 6 months, 23 days" and "923 days" are different ways to say the same gap. Dividing by 30 accumulates error. Walk the calendar month by month to get a real years-months-days breakdown.

Month ends have their own traps:

Calculation	Result
Feb 29 + 1 year	Feb 28 (the target year has no Feb 29)
Jan 31 + 1 month	Feb 28 (clamped to the last day of the month)

3. Counting workdays

Workdays are the days in a range minus Saturdays and Sundays. Public holidays are not excluded, so when a contract says "10 business days", double-check against that year's holiday calendar.

4. One-step on iPhone

Date Calculator: Day Counter 2.0 was rebuilt around these details:

1. Days between dates — days, weeks, months and years at once, an exact years/months/days breakdown, workdays and weekend days counted for you, with an optional "count the end day too".
2. Add or subtract time — years, months, weeks and days from any date, live results with the weekday, day of the year and how far away it is, plus presets for 1 week, 30 days, 90 days, 100 days, 6 months and 1 year.
3. Workdays mode — skips weekends when adding or subtracting, handy for deadlines, delivery times and notice periods (public holidays are not excluded).

English and Simplified Chinese, dark mode, iPhone and iPad, and any result can be shared in one tap.

Takeaway: decide inclusive or exclusive first, count months on the calendar rather than as 30 days, and verify holidays for workday counts.