Preventing Excel from Automatically Converting Date Strings

When writing Python macros in Excel using PyXLL, you might notice that writing a date string like "10/02/2026" ends up appearing in Excel as 2/10/2026.

Example:

from pyxll import xl_macro, XLCell

@xl_macro
def my_test():
   XLCell.from_range("Sheet1!A1").value = "10/02/2026"

Instead of showing 10 Feb 2026, Excel may display 2 Oct 2026.

Why This Happens

This is normal Excel behavior — not a PyXLL issue.

Whenever a string looks like a date, Excel automatically converts it into a real date using your system’s regional settings. The same thing happens in VBA.

How to Stop Excel from Converting the String

Option 1 (Easiest): Prefix with a Single Quote

XLCell.from_range("Sheet1!A1").value = "'10/02/2026"

Excel will:

• Store it as text

• Hide the leading '

• Not convert it to a date

Option 2: Set the Cell Format to Text First

Set the cell’s number format to "@" (Text) before assigning the value. This prevents Excel from interpreting the string as a date.

@xl_macro
def my_test():
   cell = XLCell.from_range("Sheet1!A1")
   cell.to_range().NumberFormat = "@"
   cell.value = "10/02/2026"

Best Practice

• If you want a real date, pass a Python datetime object.

• If you want a literal string, use ' or format the cell as Text first.

This avoids unexpected date swapping when using PyXLL to import CSV files or write data from Python into Excel.