Weekday Calculator
Find what day of the week any date falls on. Free online Day of the Week calculator shows weekday name, weekend status, day of year, days remaining, and week number.
About This Calculator
The Weekday Calculator (also known as a Day of the Week calculator) tells you exactly which day of the week any date falls on. Whether you need to find out what day you were born, what day a holiday lands on, or what day of the week a future event occurs, simply select the date and get instant results. This tool is useful for event planning, historical research, travel planning, and satisfying personal curiosity.
The calculator uses the standard Gregorian calendar algorithm through the JavaScript Date object and the date-fns library. When you select a date, the calculator determines the day of the week by computing the number of days since a known reference point, correctly handling leap years (years divisible by 4, except century years not divisible by 400) and all calendar boundaries. Beyond the day name, the calculator also computes the day of the year (1 to 365/366), days remaining in the year, ISO week number (1-53), and a monthly chart showing the distribution of each weekday in the selected month.
Regional Notes
India (IN): The work week in India runs Monday through Friday, with Saturday and Sunday as weekend days. The calculator uses this standard convention for all regions. Knowing the day of the week is useful for planning bank holidays, festival dates (Diwali, Holi, Eid follow lunar calendars but are observed on specific weekdays), and stock market trading days (NSE/BSE operate Monday through Friday).
United States (US): The US follows the Monday-Friday work week. Americans use this calculator for planning federal holidays (Thanksgiving is always Thursday, Memorial Day always Monday), checking wedding dates, planning vacation departures, scheduling medical appointments, and determining the day of the week for historical events.
United Kingdom (UK): The UK also follows Monday-Friday as the standard work week with Saturday-Sunday weekends. British users commonly check the day of the week for Bank Holidays (which always fall on Mondays), plan around school half-terms, check royal events and state occasions, and determine weekday schedules for postal services and council operations.
Days of the Week Etymology
The names of the days in English trace back to a blend of Roman and Germanic/Norse mythology. Sunday and Monday are named after the Sun and Moon. Tuesday (Tiw's day), Wednesday (Woden's day), Thursday (Thor's day), and Friday (Frigg's day) come from Germanic gods matching the Roman gods Mars, Mercury, Jupiter, and Venus. Saturday is the only day retaining its Roman origin — named after Saturn. Understanding the origin of weekday names helps in remembering which days correspond to which Norse or Roman deities.
The core calculation is: given a date, the day of the week is computed using the Gregorian calendar algorithm. The day index (0 for Sunday through 6 for Saturday) determines the day name. The day of the year is computed as the number of days elapsed since January 1 of the same year. The ISO week number follows the ISO 8601 standard where week 1 contains the first Thursday of the year. The monthly chart counts each day in the selected month and groups them by weekday, showing at a glance whether the month has 5 of any particular weekday.
Frequently Asked Questions
What day of the week was I born?
Enter your birth date in the calculator and it will instantly show the exact day of the week you were born on. For example, someone born on January 1, 2000 was born on a Saturday.
Is the calculator free to use?
Yes, this Day of the Week calculator is completely free to use with no registration or account required. Shareable URLs let you save and send results.
Does the calculator work for past and future dates?
Yes, the calculator works for any date in the past, present, or future. It correctly handles leap years, the Gregorian calendar, and all date boundaries.
How is the day of the week determined?
The calculator uses the standard Gregorian calendar algorithm. Internally, JavaScript Date handles date arithmetic along with the date-fns library which correctly accounts for leap years, century rules, and all calendar transitions.
What is the difference between a weekday and a weekend?
Weekdays are Monday through Friday — the standard business and school days in most countries including India, the United States, and the United Kingdom. Weekends are Saturday and Sunday, typically rest days.
What additional information does the calculator show?
Besides the day of the week, the calculator shows whether it is a weekday or weekend, the day of the year (e.g., day 204 of 366), the number of days remaining in the year, the ISO week number, and a monthly chart showing how many of each weekday appear in the selected month.
What is the ISO week number?
ISO week numbers assign each week of the year a number from 1 to 52 (or 53). Week 1 is the week containing the first Thursday of the year. This system is used internationally for business planning, payroll, and logistics.
What day of the week is today?
Select today's date in the calculator to see the current day of the week. The date input defaults to today so you can instantly see what day it is.