Excel 2013 Day of Week Calculator
Calculate the day of the week for any date using Excel 2013 formulas. Enter your date components below to see the result and get the exact formula.
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Complete Guide: Calculate Day of the Week in Excel 2013
Calculating the day of the week for any given date is a common requirement in Excel spreadsheets. Whether you’re creating schedules, analyzing temporal data, or building calendars, knowing how to determine the weekday from a date is essential. This comprehensive guide covers multiple methods to calculate the day of the week in Excel 2013, including built-in functions and mathematical algorithms.
Why Calculate Days of the Week in Excel?
- Schedule Planning: Automatically determine weekdays for appointments and events
- Data Analysis: Group and analyze data by day of week (e.g., sales trends)
- Financial Calculations: Determine business days for interest calculations
- Project Management: Create Gantt charts with proper weekday alignment
- Historical Research: Determine what day historical events occurred on
Method 1: Using Excel’s WEEKDAY Function (Simplest Method)
The WEEKDAY function is Excel’s built-in solution for determining the day of the week. In Excel 2013, this function returns a number from 1 to 7 representing the day of the week.
Syntax:
=WEEKDAY(serial_number,[return_type])
Parameters:
- serial_number: The date you want to evaluate (can be a cell reference or DATE function)
- [return_type] (optional):
- 1 (default): Numbers 1 (Sunday) through 7 (Saturday)
- 2: Numbers 1 (Monday) through 7 (Sunday)
- 3: Numbers 0 (Monday) through 6 (Sunday)
Examples:
- Basic usage (returns 1-7 where 1=Sunday):
=WEEKDAY("15-Oct-2023")Returns: 1 (Sunday) - With return_type 2 (1=Monday):
=WEEKDAY("15-Oct-2023",2)Returns: 7 (Sunday) - Using cell reference:
=WEEKDAY(A1)
Where A1 contains a date
Pro Tip: Combine with CHOOSE or INDEX functions to return day names instead of numbers:
=CHOOSE(WEEKDAY(A1),"Sunday","Monday","Tuesday","Wednesday","Thursday","Friday","Saturday")
Method 2: Using TEXT Function for Day Names
The TEXT function provides a simple way to format dates as day names without complex calculations.
Syntax:
=TEXT(value, format_text)
Examples:
- Full day name:
=TEXT("15-Oct-2023","dddd")Returns: “Sunday” - Short day name:
=TEXT(A1,"ddd")
Returns: “Sun” (where A1 contains a date) - Custom format with day and date:
=TEXT(TODAY(),"dddd, mmmm d, yyyy")
Returns: “Sunday, October 15, 2023”
| Format Code | Result | Example Output |
|---|---|---|
| “ddd” | Short day name | Sun, Mon, Tue |
| “dddd” | Full day name | Sunday, Monday |
| “ddd, mmm d” | Short day and date | Sun, Oct 15 |
| “dddd, mmmm d, yyyy” | Full date format | Sunday, October 15, 2023 |
Method 3: Zeller’s Congruence Algorithm (Mathematical Approach)
For those who prefer mathematical solutions or need to implement this in non-Excel environments, Zeller’s Congruence is an algorithm devised by Christian Zeller to calculate the day of the week for any Julian or Gregorian calendar date.
Formula for Gregorian Calendar:
h = (q + floor((13(m+1))/5) + K + floor(K/4) + floor(J/4) + 5J) mod 7
Where:
- h is the day of the week (0 = Saturday, 1 = Sunday, 2 = Monday, …, 6 = Friday)
- q is the day of the month
- m is the month (3 = March, 4 = April, …, 14 = February)
- K is the year of the century (year mod 100)
- J is the zero-based century (floor(year / 100))
Excel Implementation:
To implement Zeller’s Congruence in Excel 2013:
- Adjust January and February to be months 13 and 14 of the previous year
- Use the formula with Excel’s floor functions
=MOD(A1 + FLOOR((13*(B1+1))/5,1) + C1 + FLOOR(C1/4,1) + FLOOR(D1/4,1) + 5*D1,7)
Where:
- A1 = day (q)
- B1 = month (m, with Jan=13, Feb=14 of previous year)
- C1 = year of century (K = YEAR mod 100)
- D1 = century (J = floor(YEAR / 100))
Method 4: Using MOD Function with Date Serial Numbers
Excel stores dates as serial numbers (days since January 1, 1900), which allows for mathematical operations to determine the day of the week.
Basic Principle:
Since there are 7 days in a week, you can use the MOD function to find the remainder when dividing the date’s serial number by 7.
Formula:
=MOD(A1,7)
Where A1 contains a date. This returns:
- 0 = Sunday (1900-01-01 was a Monday, but Excel counts 1900 as a leap year incorrectly)
- 1 = Monday
- 2 = Tuesday
- 3 = Wednesday
- 4 = Thursday
- 5 = Friday
- 6 = Saturday
Adjustment for Correct Weekday:
Due to Excel’s 1900 date system bug (where it incorrectly considers 1900 a leap year), you may need to adjust the result:
=MOD(A1-2,7)
This adjustment accounts for the fact that January 1, 1900 was actually a Monday, not a Sunday as Excel’s system suggests.
Performance Comparison of Methods
| Method | Speed | Accuracy | Flexibility | Best For |
|---|---|---|---|---|
| WEEKDAY function | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐ | Most Excel calculations |
| TEXT function | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐ | Display purposes |
| Zeller’s Congruence | ⭐⭐⭐ | ⭐⭐⭐⭐⭐ | ⭐⭐⭐⭐⭐ | Mathematical implementations |
| MOD function | ⭐⭐⭐⭐ | ⭐⭐⭐⭐ | ⭐⭐⭐⭐ | Custom calculations |
Advanced Techniques
Creating a Dynamic Calendar
You can create a complete monthly calendar that automatically highlights weekends:
- Create a date series for the month
- Use WEEKDAY function to determine each date’s day of week
- Apply conditional formatting to highlight weekends
=WEEKDAY(A1,2)>5
This formula returns TRUE for Saturday and Sunday when using return_type 2 (where 1=Monday, 7=Sunday).
Calculating Business Days
To calculate the number of business days between two dates (excluding weekends and optionally holidays):
=NETWORKDAYS(start_date, end_date, [holidays])
Example:
=NETWORKDAYS("1-Oct-2023", "31-Oct-2023", Holidays!A1:A10)
Where Holidays!A1:A10 contains a list of holiday dates.
Working with Fiscal Years
Many businesses use fiscal years that don’t align with calendar years. You can create custom weekday calculations for fiscal periods:
=WEEKDAY(A1-(WEEKDAY(A1)-2),2)
This formula finds the previous Monday for any given date, useful for weekly fiscal reporting.
Common Errors and Troubleshooting
When working with day of week calculations in Excel 2013, you may encounter these common issues:
1. #VALUE! Errors
Cause: The function receives a non-date value.
Solution: Ensure your input is a valid date or date serial number. Use ISNUMBER to check:
=IF(ISNUMBER(A1), WEEKDAY(A1), "Invalid date")
2. Incorrect Day Returns
Cause: Using the wrong return_type parameter or not accounting for Excel’s 1900 date system bug.
Solution: Double-check your return_type parameter and consider using the MOD adjustment method for critical applications.
3. Two-Digit Year Issues
Cause: Excel may interpret two-digit years incorrectly (e.g., “23” as 1923 instead of 2023).
Solution: Always use four-digit years or ensure your system settings are configured correctly.
4. Time Component Interference
Cause: Dates with time components may cause unexpected results.
Solution: Use INT to remove time components:
=WEEKDAY(INT(A1))
Historical Context and Algorithmic Foundations
The calculation of weekdays from dates has a rich mathematical history. The algorithms we use today build upon centuries of calendar research:
Christian Zeller, a German mathematician, first published his congruence in 1883. The algorithm was designed to be computable by hand, making it particularly valuable before the computer age. Modern implementations in Excel maintain the algorithm’s efficiency while adding the power of electronic computation.
The Gregorian calendar, introduced by Pope Gregory XIII in 1582, established the calendar system we use today, including the rules for leap years that are essential for accurate weekday calculations across centuries.
Practical Applications in Business
Understanding how to calculate days of the week in Excel has numerous business applications:
1. Retail Analysis
Retail businesses often see different sales patterns on different days of the week. By categorizing sales data by weekday, managers can:
- Optimize staffing schedules
- Plan promotions for high-traffic days
- Analyze the impact of weekends vs. weekdays on revenue
2. Human Resources
HR departments use weekday calculations for:
- Tracking employee attendance patterns
- Scheduling shifts to ensure proper weekend coverage
- Calculating overtime for weekend work
3. Project Management
Project managers rely on accurate weekday calculations to:
- Create realistic timelines accounting for weekends
- Schedule critical path activities on appropriate days
- Track project progress by business days
4. Financial Services
Banks and financial institutions use weekday calculations for:
- Determining settlement dates for transactions
- Calculating interest over specific day counts
- Scheduling automated payments on business days
Excel 2013 Specific Considerations
Excel 2013 has some unique characteristics that affect day of week calculations:
Date System Limitations
Excel 2013 uses the 1900 date system (where January 1, 1900 is day 1), which has two important implications:
- Excel incorrectly treats 1900 as a leap year (February has 29 days)
- The maximum date is December 31, 9999
For most practical purposes, these limitations don’t affect day of week calculations for dates in the 20th and 21st centuries.
Function Availability
Excel 2013 includes all the functions needed for weekday calculations:
- WEEKDAY – The primary function for this purpose
- TEXT – For formatting dates as day names
- MOD – For mathematical approaches
- DATE – For creating dates from components
- NETWORKDAYS – For business day calculations
Performance Optimization
For large datasets in Excel 2013:
- Use array formulas sparingly as they can slow down calculation
- Consider using helper columns instead of complex nested functions
- Use Table structures for better performance with filtered data
Alternative Approaches in Other Software
While this guide focuses on Excel 2013, similar functionality exists in other spreadsheet software:
| Software | Equivalent Function | Syntax Example |
|---|---|---|
| Google Sheets | WEEKDAY | =WEEKDAY(A1) |
| LibreOffice Calc | WEEKDAY | =WEEKDAY(A1) |
| Apple Numbers | WEEKDAY | =WEEKDAY(A1) |
| JavaScript | getDay() | dateObject.getDay() |
| Python | weekday() | from datetime import datetime datetime(2023,10,15).weekday() |
Learning Resources and Further Reading
To deepen your understanding of date calculations in Excel:
Recommended books for advanced Excel users:
- “Excel 2013 Formulas” by John Walkenbach
- “Advanced Excel Essentials” by Jordan Goldmeier
- “Excel Data Analysis” by Pauline Cullingworth and Hector Guerrero
Future-Proofing Your Calculations
When creating Excel workbooks that calculate days of the week:
- Document your formulas: Add comments explaining complex calculations
- Use named ranges: Makes formulas more readable and easier to maintain
- Test edge cases: Verify calculations for leap years and century transitions
- Consider time zones: If working with international data, account for time zone differences
- Plan for Excel updates: Newer Excel versions may introduce more efficient functions
For mission-critical applications, consider:
- Creating validation checks for date inputs
- Implementing error handling for invalid dates
- Building test cases to verify calculations across different scenarios
Conclusion
Mastering day of the week calculations in Excel 2013 opens up powerful possibilities for date analysis and scheduling. Whether you use the simple WEEKDAY function, the flexible TEXT function, or the mathematical precision of Zeller’s Congruence, Excel provides robust tools for working with temporal data.
Remember that the best method depends on your specific needs:
- For quick results, use WEEKDAY or TEXT functions
- For mathematical understanding, implement Zeller’s Congruence
- For large datasets, optimize with helper columns and efficient formulas
- For display purposes, leverage Excel’s formatting capabilities
By combining these techniques with Excel’s other date functions, you can create sophisticated temporal analyses that provide valuable insights for business decision-making, historical research, or personal organization.