Enter any date and see which day of the week it falls on, whether it’s a weekend, which day of the year it is, its ISO week number, and whether the year is a leap year. Works for past and future dates alike, entirely on your device.
Pick a date to see its day of the week.
How it works
The weekday comes straight from the calendar and is shown in your language — Monday through Sunday, or ponedeljak through nedelja. Alongside it, the tool gives the ISO weekday number (1 for Monday through 7 for Sunday), which is the convention spreadsheets and code use.
The extras answer related questions in one place: the day of the year (1–366), the ISO 8601 week number with its week-year, and whether the year is a leap year. The week-year can differ from the calendar year around New Year — early January can still belong to the last week of the previous year.
Practical examples
What day was I born?
Enter a birth date like 1998-07-23 to see it was a Thursday. A quick way to answer the classic “what day of the week was I born on?”
Which weekday is a future date?
Check whether 2026-12-25 lands on a weekend before planning around it — it’s a Friday, so a long weekend is on the cards.
Finding the ISO week
For a date like 2026-01-01, the tool shows the ISO week and week-year, useful for planning against week-numbered calendars common in business and logistics.
Frequently asked questions
What does the ISO weekday number mean?
ISO numbers the days 1 to 7 starting on Monday, so Monday is 1 and Sunday is 7. This differs from the JavaScript/US convention where Sunday is 0. The tool shows the ISO number because it’s what most spreadsheets and business systems expect.
Which days count as the weekend?
Saturday and Sunday, the standard weekend in Serbia and most of the world. The tool flags a date as a weekend only for those two days; it doesn’t account for public holidays.
Why does early January sometimes show last year’s week?
ISO 8601 week 1 is the week containing the year’s first Thursday, and weeks start on Monday. So 1–3 January can fall in the final week of the previous week-year. That’s why the tool shows a week-year next to the week number.
What is the day of the year?
It’s the date’s position in the year, from 1 on 1 January to 365 — or 366 in a leap year — on 31 December. It’s handy for logs, scientific data and anything counted in ordinal days.
How do you determine a leap year?
A year is a leap year if it’s divisible by 4, except century years, which must be divisible by 400. So 2024 and 2000 are leap years, but 1900 and 2100 are not. Leap years have 366 days, with 29 February added.
Does it work for dates far in the past or future?
Yes, across the full range the calendar supports. Note that today’s Gregorian calendar wasn’t in use everywhere historically, so for dates centuries ago the weekday is the proleptic Gregorian one, which may differ from the local calendar then in use.
Is the weekday shown in Serbian?
Yes. On the Serbian version the weekday name appears in Serbian (Latin script); on the English version it appears in English. The underlying date is identical — only the label’s language changes.
Is the date I enter kept private?
Yes. Everything is computed in your browser; nothing is uploaded and analytics never receives the date.
Related tools
Days Between Dates
Count the exact days between two dates, with a weeks and calendar breakdown. Runs in your browser.
Date & time
Week Number Calculator
Find the ISO 8601 week number for any date, with the week’s Monday–Sunday range. Runs in your browser.
Date & time
Add or Subtract Days
Add or subtract days, weeks and months from a date to get the resulting date and its weekday. Runs in your browser.
Date & time
Age Calculator
Exact age in years, months and days from a birth date, plus total days lived and time until the next birthday.
Date & time
Unix Timestamp Converter
Convert a Unix timestamp to a human date (UTC and local) and back, with seconds/milliseconds detection. Runs in your browser.
Date & time
Prime Number Checker
Check whether a number is prime, with its prime factorisation and the nearest primes. Runs in your browser.
Math & education