Day of Week Calculator
Determine the day of the week for any date in history or the future. Switch between Julian and Gregorian calendar systems, view a visual calendar of the selected month, translate day names across languages, and check which years share the exact same weekday alignment.
Thursday
June 18, 2026 (Gregorian Calendar)
June 2026
| Su | Mo | Tu | We | Th | Fr | Sa |
|---|---|---|---|---|---|---|
| - | ||||||
| - | - | - | - |
Insights & Symbolism
"...is has far to go."
Known as "Thor's Day" in Norse tradition, representing the god of thunder and strength, equivalent to Roman Jupiter.
The date June 18 fell or will fall on a Thursday in the following years:
Key Features
Zeller's Congruence Precision
Uses mathematically exact Zeller Congruence formula to ensure perfect weekday results.
Dual Calendar Support
Supports Julian and Gregorian calendar modes with auto-detection for the 1582 transition gap.
Multilingual Weekday Translations
Translates weekday names across Latin, Spanish, French, German, Italian, and Sanskrit/Hindi.
100% Client-Side Privacy
Calculations run entirely in your web browser. No data is stored or sent to external servers.
Common Use Cases
Historical & Archival Research
Quickly find what weekday historical treaties, declarations, or battles occurred in the Julian or Gregorian calendars.
Birthdays & Milestones
Discover the weekday you or your family members were born on, and explore future year birthday planning.
Education & Mathematics
Study algorithm behaviors like Zeller's Congruence or Gregorian calendar leap rules for school projects.
Scheduling & Silo Alignment
Check weekdays for calendar deadlines, contract timings, or specific historical cycles.
About the Day of Week Calculator
Have you ever wondered what day of the week a historical treaty was signed, or what weekday you were born on? The Day of Week Calculator is a highly accurate tool designed to compute the day of the week for any date starting from 1 AD up to the year 9999 AD.
The Mathematical Engine: Zeller's Congruence
At the heart of this tool is Zeller's Congruence, an arithmetic algorithm formulated by Christian Zeller in 1882. The formula calculates the day of the week for any date in the Julian or Gregorian calendars. It maps the day of the month, month, and year values using modulo arithmetic. Because January and February skew calendar year-end counts, Zeller's formula treats them as months 13 and 14 of the preceding year.
The Great Calendar Shift of 1582
In 1582, Pope Gregory XIII decreed the transition from the Julian calendar to the Gregorian calendar to correct a drift in the spring equinox. To realign the solar year, ten days were omitted: October 4, 1582 (Julian calendar) was followed immediately by October 15, 1582 (Gregorian calendar).
This calculator features an automatic detection toggle to apply Julian rules for dates on or before October 4, 1582, and Gregorian rules for dates on or after October 15, 1582. This ensures perfect historical accuracy for ancient dates and documents.
Leap Year Adjustments
A solar year is approximately 365.2422 days long. Under the Julian calendar, a leap year was added every 4 years. However, this overcorrected the solar year by about 11 minutes per year. The Gregorian system refined this: years divisible by 100 are not leap years unless they are also divisible by 400. For example, the year 1900 was not a leap year in the Gregorian calendar, but 2000 was. This tool automatically handles all these intricacies under the hood.
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Frequently Asked Questions About the Day of Week Calculator
What is a Day of Week Calculator?
A Day of Week Calculator is an online utility that computes the exact weekday (e.g., Monday, Tuesday) for any date. It is commonly used to find birth weekdays, historical event days, or map future date milestones. Our calculator supports both the Gregorian and Julian calendars and works for any date from antiquity to the far future.
How does this tool calculate the day of the week?
This tool uses Zeller's Congruence, a mathematical formula developed by Christian Zeller in the 19th century. It performs modulo arithmetic on the year, month, and day values and handles all calendar leap rules and month lengths entirely locally in your browser — no server calls required.
Why did the calendar skip 10 days in October 1582?
The Julian calendar was slightly longer than the solar year, causing the calendar to drift by about 11 minutes annually. By 1582, this had accumulated to 10 days of error. Pope Gregory XIII reformed the calendar, ordering that October 4, 1582 be followed immediately by October 15, 1582, creating the Gregorian calendar. The days October 5 through October 14, 1582 never existed.
Does this calculator handle ancient dates correctly?
Yes! By default the calculator auto-detects the 1582 transition. It applies Julian calendar rules for any dates on or before October 4, 1582, and Gregorian calendar rules for subsequent dates. You can also manually lock the calendar system to always use Julian or Gregorian rules.
How do Julian and Gregorian leap year rules differ?
In the Julian calendar, every year divisible by 4 is a leap year (e.g. 1900 is a Julian leap year). In the Gregorian calendar, a year is a leap year if it is divisible by 4, unless it is also divisible by 100 — in which case it must further be divisible by 400 (e.g. 1900 is NOT a Gregorian leap year, but 2000 is).
What are "repeating years" in the calculator?
Repeating years are future years whose calendar is identical to the queried year — same day of week for every date. The calculator finds up to three such years, which is useful for reprinting old wall calendars, scheduling recurring annual events, or satisfying curiosity about when a particular year layout will occur again.
How accurate is the moon phase shown?
The moon phase is calculated using a simplified astronomical algorithm accurate to within ±1 day for most dates. The phase icon and name (New Moon, Waxing Crescent, First Quarter, etc.) are computed from the number of days since a known New Moon reference epoch. For precise scientific or nautical purposes, consult a specialist ephemeris.
Is my input date stored or sent to a server?
No. All calculations run entirely client-side using JavaScript in your web browser. No date queries, inputs, or IP addresses are ever sent to a server, ensuring complete data privacy every time you use this tool.