Add to or subtract from a date, count days between two dates, find workdays, weekdays, and week numbers — all in one free tool.
6 Calculators in OneWorkday SupportISO 8601 WeeksInstant Results
Count days between two dates
Find the number of years, months, weeks, and days between any two dates.
Add to or subtract from a date
Enter a start date and add or subtract any number of days, months, or years.
Count workdays between two dates
Counts Monday through Friday by default. Choose which weekdays count below.
Add or subtract workdays
Skip weekends (or any custom set of days) when scheduling deadlines.
What day of the week is it?
Pick any date and we’ll tell you the weekday.
Find the week number (ISO 8601)
Returns the ISO week number for any date.
Tracking expiration dates? Stop using a calculator.
Expiration Reminder tracks expiration dates for contracts, certifications, warranties, licenses, and more — and sends automatic reminders by email, SMS, or WhatsApp before things expire.
Common questions about calculating dates, workdays, and week numbers.
How does the date calculator handle months of different lengths?
When you add months, we keep the same day of the month and roll backwards if the target month is shorter (e.g. Jan 31 + 1 month = Feb 28 or Feb 29 in a leap year).
Does “Count Days” include both the start and end date?
By default we count the difference (end minus start), which excludes one of the two endpoints. Tick Include end day to add 1 and count both endpoints.
Which week-numbering standard do you use?
ISO 8601 — weeks start on Monday and week 1 is the week containing the first Thursday of the year. This is the international standard used by most business and government systems.
Can I exclude holidays from workday counts?
Not from this free calculator — it counts based on the weekdays you select. For full holiday calendars, custom work weeks, and automated deadline tracking across your whole team, book a demo of Expiration Reminder.
Can I track real expiration dates with reminders?
Yes — that’s exactly what Expiration Reminder does. Add your items once and we’ll email, SMS, or message you on WhatsApp before they expire.
This date calculator is provided for general planning purposes. Results follow standard calendar arithmetic and ISO 8601 week numbering. For automated tracking of real expiration dates across contracts, licenses, and certifications, book a demo to see how Expiration Reminder works for your team. v2
