Download "jon-server-3.3-update-04.zip" on a Windows machine.

In "apply-updates.bat" we have:

rem Calculate time stamp.
set MM=%date:~4,2%
set DD=%date:~7,2%
set YY=%date:~12,2%

On a UK machine:

echo %date%
25/01/2016

echo %date:~4,2%
1/

echo %date:~7,2%
01

echo %date:~12,2%
ECHO is on.  (the result is an empty string, so it reacts to just 'echo')

On a Dutch machine:

echo %date%
ma 25/01/2016

echo %date:~4,2%
5/

echo %date:~7,2%
1/

echo %date:~12,2%
6

In other words: the string manipulation will only work reliable if used on a United States machine. In other countries, this will not only fail to get the correct date, but will make the script break when using these as a filename.

Solution:
- do no presume everyone is US based.
- port the script use Powershell, which since Windows Vista is always available.
- use wmic:

@echo off
setlocal enabledelayedexpansion
set DT=
for /f "delims=" %%a in ('wmic OS Get localdatetime  ^| find "."') do set DT=%%a
set DT=%DT:~0,8%
echo %DT%
-> YYYYMMDD or use 2,8  to get YYMMDD if you prefer