Fix Word Mail Merge Time Format Reverting to 24-Hour Style on Output

You set a custom time format in your Word mail merge document, but the final output shows times in a 24-hour style instead of the 12-hour format you specified. This problem occurs because Word’s merge engine reads the raw time value from the data source and applies its own default formatting, ignoring the format switch you added to the merge field. This article explains why the formatting reverts, provides a reliable fix using field codes and switches, and covers related issues like date formatting and regional setting conflicts.

Why Word Mail Merge Ignores Your Custom Time Format

When you insert a time merge field, Word stores the raw value from your data source. If the data source contains a time stored as a serial number or as text, the merge engine processes it differently. For serial number times, Word defaults to the system’s short time format, which on many Windows systems is set to 24-hour style (HH:mm). Even if you click the field and apply a time format through the Ribbon, those formatting choices are not preserved during the merge. The merge engine reads the field code and applies its own formatting rules unless you add a format switch directly to the field code.

How Field Codes and Switches Work

Every merge field is represented by a field code. By default, a time merge field looks like { MERGEFIELD Time }. To control the output format, you add a format switch: \@ "h:mm AM/PM". This switch tells Word exactly how to display the time, overriding both the data source format and the system regional settings. Without this switch, Word uses the default short time pattern from Windows, which is often 24-hour style.

Text-Based Time Values

If your data source contains time values stored as text such as “14:30”, the format switch still works because Word can parse common time text patterns. However, if the text is irregular, you may need to pre-process the data in the source file or use a calculated field in the merge document.

Steps to Add a Format Switch to a Time Merge Field

Follow these steps to force a 12-hour time format with AM/PM in your mail merge output. The process works in Word 2016, Word 2019, Word 2021, and Word for Microsoft 365.

1. Open the mail merge document and show field codes
   Press Alt+F9 on your keyboard. This toggles the display from merge field results to the underlying field codes. You will see something like { MERGEFIELD Time } instead of a time value.
2. Locate the time merge field
   Scroll through the document and find the field code that corresponds to the time. If you have multiple time fields, repeat the next step for each one.
3. Add the format switch
   Click inside the field code just after the field name. Type a space, then add the following switch: \@ "h:mm AM/PM". The complete field code should look like this: { MERGEFIELD Time \@ "h:mm AM/PM" }. Make sure you include the backslash and the @ symbol.
4. Close field codes view
   Press Alt+F9 again to hide the field codes and see the formatted result. If you have preview results enabled, you should now see times displayed as 2:30 PM instead of 14:30.
5. Run a test merge
   Click Mailings > Preview Results to verify the formatting for several records. Then complete the merge by clicking Finish & Merge > Edit Individual Documents or Print Documents.

Alternative Format Switches

You can customize the time output by changing the picture string inside the switch. Common examples include:

• \@ "h:mm:ss AM/PM" for hours, minutes, and seconds with AM/PM
• \@ "h:mm" for 12-hour time without AM/PM
• \@ "HH:mm" to force 24-hour time explicitly

If the Format Switch Does Not Work

In some cases, the format switch does not change the output. This usually happens when the data source contains time values stored as text in a non-standard format, or when the merge field is nested inside another field such as an IF or a calculation.

“Time Still Shows as 14:30 After Adding the Switch”

Check the data source. Open the Excel sheet or Access table that supplies the data. Ensure the time column is formatted as Time, not as Text. If it is text, convert it using Excel’s TIMEVALUE function or change the column format to Time. Then refresh the merge document by clicking Mailings > Select Recipients > Use an Existing List and re-selecting the file.

“Date Merge Fields Also Show Wrong Format”

The same principle applies to dates. Add the switch \@ "MMMM d, yyyy" to a date merge field to get output like “March 15, 2025”. Without a switch, Word uses the system short date format, which may display as “3/15/2025” or “15/03/2025” depending on your region.

“The Switch Works in Preview but Not in Final Output”

This can occur if you use the Finish & Merge > Send Email Messages option. Some email merge settings strip field formatting. Use Finish & Merge > Edit Individual Documents instead, then copy the output to your email manually.

Mail Merge Time Format: Field Code Switch vs Data Source Format

Item	Field Code Switch	Data Source Format
Control location	Inside the Word document field code	In the source file (Excel, Access, CSV)
Format override	Overrides all other formatting instructions	Ignored by Word during merge unless switch is present
Requires field code editing	Yes, Alt+F9 is needed	No, but must match a parseable time pattern
Works with text time values	Yes, if the text is a standard time pattern	Not recommended; text often causes formatting loss
Affected by Windows region settings	No, the switch is explicit	Yes, the default short time format is used
Best practice	Always add the switch for consistent output	Keep as Time serial number for reliable parsing

Conclusion

You can now force Word to display times in 12-hour AM/PM format by adding the \@ "h:mm AM/PM" switch to the merge field code. This method works regardless of your Windows regional settings or the data source formatting. After fixing the current document, review any other date or time merge fields and add the appropriate switches. As an advanced tip, consider saving a template document with the switches already applied so you do not have to edit field codes for every new merge.