The filename, directory name, or volume label syntax is incorrect.

The filename, directory name, or volume label syntax is incorrect. is Windows system error 123 (ERROR_INVALID_NAME). The path is not a valid Windows name at all, so Windows does not even look for it. File and folder names cannot contain < > : " / \ | ? *; a colon is only allowed after the drive letter. Print the expanded path and remove the character that does not belong.

Reproduce it

mkdir "build<1>" 2>&1
mkdir "logs|old" 2>&1
mkdir "logs-2026-10-21"
dir /b /ad logs*

The filename, directory name, or volume label syntax is incorrect.
The filename, directory name, or volume label syntax is incorrect.
logs-2026-10-21

Common sources of bad names

A date-based name that is valid on every locale:

for /f %%d in ('powershell -NoProfile -Command "Get-Date -Date 2026-10-21 -Format yyyy-MM-dd"') do set "STAMP=%%d"
mkdir "backup-%STAMP%"
dir /b /ad backup-*

backup-2026-10-21

In a real script, drop -Date 2026-10-21 to use today's date. %DATE% itself is not portable: its format follows the user's regional settings and usually contains /.