The two ways to count
There are two honest answers to "how many days from 4 July to 25 December", and they differ by one:
- Calendar days between — the number of nights, or full days, that separate the two dates. The start date is not counted; the end date is. This is the default almost everywhere.
- Days including both ends — you add one, because you're counting the first day and the last day. This is what you want for a stay, a rental, a trip length, or "how many days am I on site".
Neither is wrong. Decide which one the question is asking before you start, because every method below gives you the "between" figure and you add one at the end if you need the inclusive count.
Method 1: count forward through the calendar
Best when the two dates are close together, or in the same year. Move from the start date to the end date in chunks and add the chunks up:
- Days left in the start month — subtract the start day from the number of days in that month.
- The full months in between — add their lengths (30, 31, 28 or 29 for February).
- The day number in the end month.
For 4 July to 25 December 2026: July has 31 days, so 31 − 4 = 27 days left in July. The full months between are August (31), September (30), October (31) and November (30) — that's 122. Then 25 days into December. Total: 27 + 122 + 25 = 174 days.
Method 2: convert each date to a day-number and subtract
Best when the dates are far apart or in different years. Give each date its ordinal day of the year — 1 for 1 January, 32 for 1 February, and so on — then subtract.
4 July 2026 is day 185 of the year. 25 December 2026 is day 359. Same year, so: 359 − 185 = 174 days — the same answer Method 1 gave.
Across years, add 365 for each full year between the dates and then add one more day for every 29 February inside the span. From 1 March 2023 to 1 March 2025 is 365 + 366 = 731 days, because 2024 was a leap year and its 29 February sits inside the range.
Counting in weeks, months and years instead
Once you have the day count, weeks is just division: 174 ÷ 7 = 24 weeks with 6 days left over.
Months and years are different — you can't divide, because months aren't all the same length. You count them the calendar way: whole years first, then whole months, then leftover days. 4 July to 25 December is 0 years, 5 months, 21 days (July 4 → December 4 is five months; December 4 → 25 is 21 days). This is the same borrow-and-carry idea used to work out an exact age.
Business days only — excluding weekends and holidays
For contracts, notice periods and "net 30" invoice terms, what's often meant is working days. The shortcut: every 7-day block contains exactly 5 weekdays. So for a span of N days, start with 5 × (N ÷ 7), then add the leftover weekdays from the partial week, and finally subtract any public holidays that fall on a weekday inside the range.
174 days is 24 whole weeks (120 working days) plus 6 leftover days. Depending on which weekday the span starts on, those 6 add 4 or 5 more working days — so roughly 124-125 before holidays. Independence Day 2026 falls on a Saturday and Christmas Day on a Friday, so only Christmas comes out of the count here. Hand estimates get fiddly fast, which is what the calculator's business-day mode is for.
Leap years, and why two calculators disagree by a day
A year is a leap year if it divides by 4 — unless it's a century year, which must divide by 400. 2000 was a leap year; 1900 and 2100 are not. Any span that steps over a 29 February is one day longer than the same span in a common year, and forgetting that is the single most common hand-count error.
When two tools disagree by a day for the same two dates, it's almost always one of these:
- End date included or not. One tool counts the last day, the other doesn't. This is the "+1" from the top of the article.
- A missed leap day. One handled 29 February inside the range and the other didn't.
- Time zones. One is using local time and the other UTC, which can shift a date across midnight.
- Month-length in the borrow. For the years-months-days breakdown, tools sometimes borrow a different month's length and land a day apart.
A worked example, start to finish
Question: how many days from 4 July 2026 to 25 December 2026, and how many working days?
| Step | Working | Result |
|---|---|---|
| Days left in July | 31 − 4 | 27 |
| Whole months between | 31 + 30 + 31 + 30 | 122 |
| Days into December | — | 25 |
| Calendar days between | 27 + 122 + 25 | 174 |
| Including both ends | 174 + 1 | 175 |
| In weeks | 174 ÷ 7 | 24 weeks, 6 days |
| In months | calendar count | 5 months, 21 days |
The date calculator returns all of these at once, marks the span on a timeline, and gives the business-day figure with or without US federal holidays.
Frequently asked questions
How do I calculate the number of days between two dates?
Either count forward — days left in the start month, plus the whole months between, plus the day-number in the end month — or give each date its day-of-year number and subtract, adding 365 for each full year between and one more day for each 29 February in the span.
Should I count both the start and end date?
By default, no — the standard "days between" figure counts the nights, so the start date is excluded and the end date included. Add one day when you need both the first and last day counted, such as the length of a trip or a rental period.
How many days are there between two dates in different years?
Take the end date's day-of-year minus the start date's day-of-year, then add 365 for every full year between them. Add one extra day for each 29 February that falls inside the range.
How do I count only the working days between two dates?
Multiply the whole number of weeks in the span by 5, add the leftover weekdays from the partial week, then subtract any public holidays that land on a weekday inside the range. A calculator with a business-day mode does the weekday and holiday bookkeeping for you.
Why do two date calculators give me different answers?
Usually one includes the end date and the other doesn't, one missed a leap day, or they're using different time zones. For the years-months-days breakdown, they can also borrow a different month's length and land a day apart.