Date Number Calculator
Number of Days Calculator works out Days between and Days counting both dates from Start date, End date and Count the end date as a whole day. The default figures on this page give days between of 987 days; change any entry and the result, the working and the sources update together.
Your figures
Updates as you typeHow this is worked out
6 steps
- Start 2024-01-01 (Monday), end 2026-09-14 (Monday).
- Elapsed days = day number of 2026-09-14 minus day number of 2024-01-01 = 987.
- Calendar walk: 2024-01-01 + 2 year(s) + 8 month(s) + 13 day(s) = 2026-09-14.
- 987 days = 141 week(s) and 0 day(s).
- Decimal years = 987 / 365.2425 (mean Gregorian year) = 2.7023.
- Business days 2024-01-01 to 2026-09-14 inclusive = 706 weekday(s) - 29 holiday(s) = 677.
Holidays in the spantable
Its 10 worked examples are re-run on every release, last on 15 September 2026. What changed
Sources and references
6 sources
What the Number of Days Calculator calculates
Days, weeks, months and years between two calendar dates, with the calendar breakdown, the business-day count and the weekday of each date; it also measures between two date-and-time instants, counts the time elapsed since a date up to today, reports length of service, and lists the sobriety milestones passed.
How to use this Number of Days Calculator
Enter Start date, End date, Count the end date as a whole day and Holidays to exclude from business days. Days between updates as you type. Change one figure at a time to see what drives the result.
How the result is worked out
Open “How this is worked out” beside the result for the step-by-step calculation behind Days between, Days counting both dates and Whole years.
The method follows ISO 8601-1:2019, Date and time - Representations for information interchange, Howard Hinnant, chrono-Compatible Low-Level Date Algorithms (days_from_civil), Microsoft Excel NETWORKDAYS function specification, 5 U.S.C. 6103 - Federal legal public holidays and Alcoholics Anonymous sobriety chip practice (24 hours; 30, 60 and 90 days; 6 and 9 months; 1 year, 18 months and each year after).
What you can compare
Change one input at a time to see how it affects Days between, Days counting both dates and Whole years. The inputs you can vary are Start date, End date, Count the end date as a whole day and Holidays to exclude from business days.
Results are general information, not financial, tax, legal, medical or engineering advice. Check any decision that matters with a qualified professional.
See something wrong? Report a problem with this calculator
Frequently asked questions
How to calculate the number of days?
Days, weeks, months and years between two calendar dates, with the calendar breakdown, the business-day count and the weekday of each date; it also measures between two date-and-time instants. Open “How this is worked out” beside the result to see each step for your own figures.
What app can I use to calculate days?
It needs Start date, End date, Count the end date as a whole day and Holidays to exclude from business days. Nothing else is required, and the figures stay in your browser.
How to calculate how many days from a date?
The result gives Days between, Days counting both dates, Whole years, Extra months, Extra days and Extra hours, each labelled with its unit so the figure can be read on its own.
How to calculate the number of days in a year?
The page opens with worked default figures: days between of 987 days. Replace them with your own and every figure updates as you type.
How can I calculate the number of days between two dates?
The method comes from ISO 8601-1:2019, Date and time - Representations for information interchange, Howard Hinnant, chrono-Compatible Low-Level Date Algorithms (days_from_civil) and Microsoft Excel NETWORKDAYS function specification, listed in full under Sources so the figures can be checked against the original.
What information do I need for the Number of Days Calculator?
You need Start date, End date, Count the end date as a whole day and Holidays to exclude from business days. The page opens with default figures that give days between of 987 days, so you can see the scale before entering your own.