This tutorial delves into the intricacies of Excel's MONTH and EOMONTH functions. Through numerous formula examples, you'll learn to extract month information from dates, determine the first and last days of any month, convert between month names and numbers, and much more.

Previously, we explored weekday calculations. Now, we'll focus on the larger time unit of months and the Excel functions designed for this purpose.

This tutorial covers:

• Excel MONTH function: Syntax and applications.
• Extracting month numbers from dates.
• Extracting month names from dates.
• Converting between month numbers and names.
• Determining the last day of a month (using EOMONTH).
• Finding the first day of a month.
• Calculating the number of days in a month.
• Summing data by month.
• Conditional formatting of dates based on month.

Excel MONTH Function: Syntax and Usage

Excel's MONTH function efficiently extracts the month from a date, returning a number from 1 (January) to 12 (December). Compatible with Excel versions 2000 and later, its syntax is straightforward:

MONTH(serial_number)

where serial_number represents any valid date. While =MONTH(DATE(2015,3,1)) correctly returns 3 (March), using text input like =MONTH("1-Mar-2015") also works, though direct cell referencing is generally preferred for clarity and to avoid potential issues in complex formulas. For instance, =MONTH(A1) retrieves the month from cell A1, and =MONTH(TODAY()) provides the current month's number.

Extracting Month Numbers from Dates

Several methods exist for obtaining month numbers:

• MONTH Function: =MONTH(A2) (month from A2), =MONTH(DATE(2015,4,15)) (returns 4 for April).
• TEXT Function: =TEXT(A2, "m") (month number without leading zero), =TEXT(A2,"mm") (month number with leading zero). Remember, the TEXT function returns text strings, not numbers, which may affect subsequent calculations.

The image below illustrates the output of these formulas, highlighting the numerical (right-aligned) vs. text (left-aligned) results.

Extracting Month Names from Dates

To obtain month names instead of numbers, use the TEXT function with different codes:

• =TEXT(A2, "mmm") (abbreviated name, e.g., Jan), =TEXT(A2,"mmmm") (full name, e.g., January).

Alternatively, for display purposes only (without affecting cell functionality as dates), format cells directly using "mmm" or "mmmm" in custom number formatting.

Converting Month Numbers to Names

To convert month numbers (1-12) to names, use these formulas (where A2 holds the month number):

For abbreviated names: =TEXT(A2*28, "mmm") or =TEXT(DATE(2015, A2, 1), "mmm")

For full names: =TEXT(A2*28, "mmmm") or =TEXT(DATE(2015, A2, 1), "mmmm")

These formulas leverage the fact that Excel treats 1 as January 1st, 1900. Multiplying by 28 provides a date within the correct month.

Converting Month Names to Numbers

Use =MONTH(DATEVALUE(A2 & "1")) (where A2 contains the month name) to convert month names to numbers. DATEVALUE converts the text to a date serial number, and MONTH extracts the month number.

Getting the Last Day of the Month (EOMONTH Function)

The EOMONTH(start_date, months) function returns the last day of a month. start_date is the starting date, and months is the offset (positive for future, negative for past). =EOMONTH(A2, 0) gives the last day of the month in A2. =EOMONTH(TODAY(),0) provides the last day of the current month.

Finding the First Day of the Month

Several methods exist to find the first day:

• Using the month number: =DATE(year, month_number, 1)
• From a date: =DATE(YEAR(A2), MONTH(A2), 1)
• Based on the current date: =EOMONTH(TODAY(),-1) 1 (current month), =EOMONTH(TODAY(),0) 1 (next month).

Calculating the Number of Days in a Month

There's no dedicated function, but these formulas work:

• Using the month number: =DAY(DATE(year, month_number 1, 1) - 1)
• From a date: =DAY(EOMONTH(A1, 0))

Summing Data by Month

Use SUMIF with a helper column containing month numbers (=MONTH(A2)), or use SUMPRODUCT((MONTH($A$2:$A$15)=$E2)*($B$2:$B$15)) (dates in A, values in B, month number in E2).

Conditional Formatting Based on Month

Use conditional formatting rules based on formulas like =MONTH($A2)=MONTH(TODAY()) (highlight current month) or =AND(OR(DAY($A2)=25, DAY($A2)=31), MONTH(A2)=12) (highlight Christmas/New Year's).

The MONTH function's versatility extends far beyond its initial appearance. This tutorial provides a comprehensive foundation for leveraging its capabilities within your Excel work.

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