VBA & Macro Problems

Why VBA Format(1, 'mmm') Returns December and How to Fix It

Aamir Naveed Akram Oct 8, 2026 870 views

Question details

The user is trying to convert a numeric month value into an abbreviated month string, but the Format function returns an unexpected month.

Why VBA Format(1, 'mmm') Returns December

Product: Excel VBA
Device & OS: not provided
Scenario: Converting an integer representing a month (such as 1 for January) into its corresponding abbreviated name (Jan) or full name (January) using a VBA macro.
Observed behavior: Using Format(1, "mmm") returns 'December' or 'Dec' instead of the expected 'January' or 'Jan'.

Before you start

Verify whether your input variable is a simple integer (1-12) or an actual Date serial number, as VBA handles these two data types differently when applying formats.

Solution 1Recommended

Use the VBA MonthName Function (Recommended)

The most direct and reliable way to get a month name from an integer (1 to 12) is using the built-in MonthName function.

When you pass a simple integer like 1 to the Format function with 'mmm' or 'mmmm', VBA assumes it is a date serial number. In the VBA date system, the serial number 1 corresponds to December 31, 1899. This is why formatting the number 1 directly returns 'December'.

To fix this, you should use the MonthName function, which is specifically designed to translate month integers into their corresponding text names.

Open the VBA Editor

Press Alt + F11 in your spreadsheet application to open the VBA Editor, and locate the module containing your code.

Locate the problematic Format function

Find the line of code using the Format function, such as: result = Format(PreviousMonth, "mmm")

Replace Format with MonthName

Change the code to use MonthName instead. To get the abbreviated name ('Jan' for 1), use: result = MonthName(1, True)

Get the full month name

If you need the full month name ('January' for 1), simply omit the second argument or set it to False: result = MonthName(1)

Use the VBA MonthName Function (Recommended)

Understanding the Abbreviate Parameter: The second argument in MonthName is a boolean for abbreviation. Setting it to True returns a three-letter abbreviation ('Jan'), while False returns the full string ('January').

Solution 2

Construct a Valid Date for the Format Function

If you must use the Format function for a specific reason, you can construct a complete date first using the DateSerial function so VBA formats the correct month.

Write and Run VBA Macros Seamlessly in WPS Office

WPS Office provides robust support for writing and running VBA macros. You can edit your code, use functions like MonthName, and automate tasks in WPS Spreadsheet exactly as you would in other major office suites.

1. Open WPS Spreadsheet: Launch WPS Office and open your workbook in the Spreadsheet application.
2. Access the Macro Editor: Go to the Tools tab on the ribbon and click on 'Macro', or simply press Alt + F11 to open the built-in VBA Editor.
3. Update your VBA Code: Replace any instance of Format(1, "mmm") with MonthName(1, True) to ensure correct date formatting.
4. Run your Macro: Press F5 or click the Run button to execute your code and verify the correct month names are generated.

Fully compatible with Microsoft Excel VBA formats and scriptsBuilt-in Macro Editor for debugging and writing code seamlesslyAccurately processes built-in VBA functions like MonthName and FormatLightweight, fast, and free to download

microsoft office alternative - wps office

Frequently Asked Questions

Why does the number 1 translate to December in VBA?

VBA stores dates as sequential serial numbers starting from late 1899. The serial number 1 represents December 31, 1899. Therefore, when you format the number 1 to extract the month, VBA looks at that 1899 date and returns December.

How do I get the current month's name in VBA?

You can use MonthName(Month(Date)) to extract the current month number from today's system date and convert it directly into the full month name.

Does the MonthName function work for month numbers above 12?

No, the MonthName function strictly accepts integers from 1 to 12. Passing a number outside this range (like 0 or 13) will result in an 'Invalid procedure call or argument' runtime error.

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