How to Date Is Same Month in Excel

Learn multiple Excel techniques to determine whether two dates fall in the same month, complete with step-by-step examples, business-grade scenarios, troubleshooting guides, and best practices.

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11 min read • Last updated: 7/2/2025

How to Date Is Same Month in Excel

Why This Task Matters in Excel

Business analysts, accountants, project managers, and anyone who works with time-based data often need to know whether two dates fall in the same calendar month. For instance, a finance team might want to group sales invoices that belong to the same accounting period; a human-resources analyst could need to verify whether an employee’s start date and benefit-eligibility date coincide in the same month; or a supply-chain manager might compare the expected delivery date of an order with the shipped date to confirm they occurred within the same billing cycle. In all of these situations, a quick yes/no answer to “same month?” drives reporting logic, conditional formatting, and downstream calculations.

Excel is exceptionally good at handling dates: behind every date lies a sequential serial number, which means you can harness arithmetic, logical comparison, and text extraction to slice and dice date information in many ways. Checking “same month” seems trivial at first glance, yet nuances arise when the dates sit in different years (January 2023 versus January 2024), when the data set contains mixed true dates and text-looking dates, or when you need to process thousands of rows efficiently.

Failing to test for “same month” correctly can result in mis-grouped pivot tables, overstated or understated period totals, or regulatory compliance problems (e.g., revenue recognized in the wrong period). In addition, this skill connects to other core Excel workflows: period-over-period variance analysis, time-series forecasting, and dynamic dash-boarding frequently rely on accurate period grouping. Mastering multiple approaches—simple functions for quick checks, more robust formulas for edge cases, and scalable solutions for large data models—will strengthen your overall date-handling proficiency in Excel.

Best Excel Approach

The most reliable, universal method for confirming that two dates belong to the same month and the same year is to compare both the MONTH and YEAR portions simultaneously. A single comparison of MONTH values alone can give a false positive when dates cross years (for example, 14-Jan-2023 and 09-Jan-2024 both yield MONTH = 1). Therefore, the recommended formula combines the logical AND function with the YEAR and MONTH functions:

=AND(YEAR(A2)=YEAR(B2), MONTH(A2)=MONTH(B2))

Why this approach is best:

  1. Explicit year safeguard – Prevents cross-year misclassification.
  2. Native functions – YEAR and MONTH are available in every Excel version since 1995, ensuring maximum backward compatibility.
  3. Logical clarity – Anyone auditing the worksheet can instantly read the intent.
  4. Vector-friendly – The formula handles entire columns efficiently and spills correctly into dynamic array contexts.

Alternative shorthand exists for quick, same-year datasets:

=MONTH(A2)=MONTH(B2)         'Assumes data never spans multiple years

But the longer AND construct is safer in production models. Another alternative that packs month and year into one comparable number is:

=TEXT(A2,"yyyymm")=TEXT(B2,"yyyymm")

This method can be faster to type but is text-based and a bit slower on massive datasets; however, it works beautifully for multi-column VLOOKUP or XLOOKUP keys because it converts a date into a sortable yyyymm code.

Parameters and Inputs

When implementing any “same month” test, you must understand the nature of your inputs:

  1. Date Cells – Inputs must be true Excel dates (serial numbers). If your data arrives as “01/15/2023” stored as text, wrap the cell in VALUE or DATEVALUE first, or use Power Query to convert types.
  2. Data Types – YEAR and MONTH expect numeric serial date values. Text throws a #VALUE! error.
  3. Calendar System – Excel for Windows defaults to the 1900 system; Excel for Mac might optionally use 1904. Mixing systems rarely happens nowadays but can shift serial dates by 1,462 days; verify settings under Options > Advanced > When calculating this workbook.
  4. Optional Boolean Output – The AND formula returns TRUE or FALSE. Wrap it in IF to yield custom wording or numeric flags:
    =IF(AND(YEAR(A2)=YEAR(B2),MONTH(A2)=MONTH(B2)),"Same","Different")
    
  5. Blank Cells – YEAR(blank) or MONTH(blank) returns 0 and can trigger false TRUEs. Use IF or COUNT functions to guard:
    =IF(OR(A2="",B2=""),"",AND(YEAR(A2)=YEAR(B2),MONTH(A2)=MONTH(B2)))
    
  6. Offset Tests – Sometimes you need to compare a single date against the current month of NOW(). Use TODAY() or EOMONTH(TODAY(),0) accordingly.

Step-by-Step Examples

Example 1: Basic Scenario—Invoice Entry Versus Billing Date

Imagine a simple table where column A contains “Invoice Date” and column B contains “Billing Date.” You want to highlight mismatches.

Sample data
[A1:B6]

Invoice Date    Billing Date
12-Jan-2024     12-Jan-2024
23-Jan-2024     02-Feb-2024
29-Feb-2024     29-Feb-2024
03-Mar-2024     28-Feb-2024
15-Apr-2024     15-Apr-2024

Step 1: Enter the formula in C2:

=AND(YEAR(A2)=YEAR(B2),MONTH(A2)=MONTH(B2))

Step 2: Copy down. Results: TRUE, FALSE, TRUE, FALSE, TRUE.

Step 3: Apply conditional formatting to column B: Home ► Conditional Formatting ► New Rule ► Use a formula…

=NOT(AND(YEAR($A2)=$YEAR($B2),MONTH($A2)=MONTH($B2)))

Format fill color red. Every mismatched billing month lights up.

Why it works: YEAR and MONTH extract components; AND only returns TRUE when both match; NOT flips it for formatting. This ensures visual auditing before month-end close.

Variation—numeric flag: wrap in IF to produce 1/0 codes for summing mismatches.
Troubleshooting tip: If your TRUE/FALSE returns spill as “0” or “-”, check the cell format; set to General or Boolean.

Example 2: Real-World Application—Subscription Start vs. Renewal Across Large Data Set

Scenario: A SaaS company tracks [50,000] customer subscriptions. Column C stores the subscription start date, column D contains the next renewal date. Operations needs a pivot table counting customers whose renewal falls in the same calendar month as the start, signaling potential configuration errors.

Data set note: This file might sit in an Excel table named tblSubs.

Step 1: Add a calculated column in the table:

=--(TEXT([@StartDate],"yyyymm")=TEXT([@RenewalDate],"yyyymm"))

The double unary minus (--) converts TRUE/FALSE into 1/0 integers, optimizing aggregation speed.

Step 2: Create a Pivot Table. Place the 1/0 field (“SameMonthFlag”) in Values (sum). The pivot quickly totals misconfigurations.

Step 3: Slicers & timelines—hook a Timeline slicer to the RenewalDate column so stakeholders can filter by year-quarter and instantly see monthly-alignment issues.

Business impact: Automatically catching same-month renewals prevents revenue recognition errors and churn mis-forecast.

Performance considerations: When using 50 k + rows, TEXT() can be slower than YEAR/MONTH. If speed lags, revert to the AND(YEAR,MONTH) approach or push the transformation to Power Query.

Edge cases addressed: Subscriptions with lifetime licenses store no RenewalDate (blank). Wrap formula inside IF(ISBLANK([@RenewalDate]),,calculation) to avoid zeros miscounting.

Example 3: Advanced Technique—Dynamic Arrays and Multiple Comparisons

Objective: Compare one “reference” date in E2 against an entire list in column A and return only those dates that match the month. Then spill the results into adjacent columns.

Sample data: Dates in [A2:A20] covering a two-year period. Reference date = 15-May-2024 in E2.

Step 1: Build a helper column F2:

=LET(
   dates,A2:A20,
   ref,E2,
   sameMonth, (YEAR(dates)=YEAR(ref))*(MONTH(dates)=MONTH(ref)),
   FILTER(dates,sameMonth)
)

Explanation:

  • LET assigns readable variable names.
  • The logical test produces an array of TRUE/FALSE which FILTER uses to return only matching rows.

Step 2: To bring back corresponding values in column B (e.g., sales amounts), expand LET:

=LET(
   dates,A2:A20,
   sales,B2:B20,
   ref,E2,
   sameMonth,(YEAR(dates)=YEAR(ref))*(MONTH(dates)=MONTH(ref)),
   CHOOSE({1,2}, FILTER(dates,sameMonth), FILTER(sales,sameMonth))
)

CHOOSE assembles a 2-column spill: dates and their sales.

Performance optimization: A single evaluation inside LET ensures YEAR/MONTH compute once. This matters when arrays reference [A:A] entire columns.

Error handling: If no dates match, FILTER returns #CALC!. Use IFERROR(FILTER(…),“None”) to display “None”.

Professional use case: Data analysts building dashboards in Office 365 can instantly generate dynamic drill-downs by month without helper columns or pivot tables.

Tips and Best Practices

  1. Year safeguard first – Train yourself to always pair MONTH with YEAR unless you are absolutely certain the dataset is confined to one year.
  2. Use Excel Tables – Converting your range to a table (Ctrl+T) enables structured references ([InvoiceDate]) that auto-expand formulas and reduce absolute/relative errors.
  3. Let Excel store true dates – Before a “same month” test, cleanse imported CSV data using Power Query’s “Data Type ► Date” step to convert text to dates.
  4. Leverage boolean math – Multiplying two TRUE/FALSE arrays (TRUE = 1, FALSE = 0) can replace AND in array contexts for faster calculation, as shown inside LET.
  5. Conditional formatting preview – Use Evaluate Formula (Formulas ► Evaluate) to step through your AND condition when formatting doesn’t highlight the expected cells.
  6. Off-by-one pitfalls – If you subtract dates to measure month intervals, remember that not all months have 30 days; rely on EOMONTH or DATEDIF(\"m\") rather than 30-day assumptions.

Common Mistakes to Avoid

  1. Ignoring the year – Using MONTH alone can lead to January-2023 vs January-2024 false TRUEs. Always combine with YEAR for multi-year data.
  2. Comparing text to dates – Users often paste data from web pages; the cell shows 1-Feb-2024 but is stored as text. YEAR(\"1-Feb-2024\") triggers #VALUE!. Ensure numeric date types.
  3. Blank cells yielding zeros – YEAR(\"\") returns 0, MONTH(\"\") returns 0, which may mistakenly equate two blanks as “same month.” Guard with IF or use COUNT.
  4. Locale-dependent TEXT formats – TEXT(A1,\"mmm\") might return “Mai” on German systems, breaking comparisons with “May.” Always use invariant \"yyyymm\" or numeric YEAR/MONTH.
  5. Whole-column references in volatile workbooks – Using YEAR(A:A) in older Excel versions recalculates every cell and slows performance. Restrict ranges to used rows or switch to dynamic arrays + LET.

Alternative Methods

Different approaches achieve the same goal. The table below summarizes key options:

MethodFormula ExampleProsConsBest For
YEAR + MONTH + AND`=AND(`YEAR(A2)`=YEAR(`B2),MONTH(A2)`=MONTH(`B2))Clear logic, version-agnosticLong to typeEveryday finance models
TEXT to yyyymm`=TEXT(`A2,\"yyyymm\")`=TEXT(`B2,\"yyyymm\")Compact, creates join keysText conversion slower, locale riskKeys for XLOOKUP / Power Query merges
INT(EOMONTH) trick`=EOMONTH(`A2,0)`=EOMONTH(`B2,0)Single function, ignores day valueLess readable; EOMONTH not in Excel 2003Advanced analysts, large arrays
DATEDIF(\"m\")`=DATEDIF(`A2,B2,\"m\")=0Works for month span testDATEDIF undocumented; fails with reversed datesCross-month age checks

When speed matters in gigantic data models, the EOMONTH comparison is often fastest because EOMONTH does one serial calculation and avoids text functions:

=EOMONTH(A2,0)=EOMONTH(B2,0)

EOMONTH strips any day component by jumping to the last day of the month for both dates, so equality implies same yyyymm. However, EOMONTH is unavailable in Excel 2007 Starter and earlier than Excel 2007. Migrating an older workbook? Stick with YEAR/MONTH.

FAQ

When should I use the YEAR + MONTH + AND method?

Use it whenever your data can cross years, you need clear audit trails, and workbook compatibility down to Excel 2007 is required. It is the safest all-purpose formula.

Can this work across multiple sheets?

Absolutely. Just qualify the references:

=AND(YEAR(Sheet1!A2)=YEAR(Sheet2!B2), MONTH(Sheet1!A2)=MONTH(Sheet2!B2))

For many-row comparisons, consider adding the formula to each sheet and then linking to avoid thousands of cross-sheet calls that slow calculation.

What are the limitations?

The main constraints are data type fidelity (dates vs text) and calculation overhead when referencing massive ranges. Additionally, functions such as TEXT introduce locale dependence, and EOMONTH is unavailable in older versions.

How do I handle errors?

Wrap the formula in IFERROR or check blanks first:

=IF(OR(A2="",B2=""),"Missing date", IF(AND(YEAR(A2)=YEAR(B2),MONTH(A2)=MONTH(B2)),"Same","Different"))

For large tables, prefer Data Validation on input columns to enforce date entries at the source.

Does this work in older Excel versions?

YEAR and MONTH exist back to Excel 95. AND also exists. EOMONTH was added in Excel 2007. Dynamic arrays, LET, and FILTER require Office 365 or Excel 2021+. Choose methods accordingly.

What about performance with large datasets?

On 100,000 + rows, avoid volatile functions and whole-column references. The Boolean mathematical approach (YEAR(range)=...)*(MONTH(range)=...) within LET can be 20-30 % faster. Push heavy transformations to Power Query or Power Pivot when feasible.

Conclusion

Knowing how to test whether two dates fall in the same month is a deceptively simple yet mission-critical skill in Excel. It underpins accurate period grouping, ensures financial statements are correct, and supports dynamic dashboards that stakeholders trust. By leveraging the robust YEAR + MONTH + AND formula—supplemented with TEXT, EOMONTH, or dynamic array techniques—you can tackle everything from quick one-off checks to enterprise-scale data models. Add these methods to your Excel toolbox, practice with real datasets, and you will dramatically reduce time spent troubleshooting period errors while boosting the reliability of your analyses. Continue exploring related topics such as date offsets, quarter grouping, and rolling period calculations to expand your temporal data mastery.

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