PHP and so Blogless provide date formatting through the strftime() function. These directives are known to work with Linux and Windows:
%A - the day of the week, e.g. "Sunday"
%d - the numeric day of the month with leading zero, e.g. "05"
%B - the month, like "December"
%Y - the full year, like "1999"
%S - gives the numeration characters after the day, like 1st, 2nd, 3rd, 5th, ...
PHP's strftime is just a thin wrapper around the underlying operation system function - and unfortunately there is no standard. So you need to have a look what directives are supported by your specific operating system and use only these.
If your date in the article disappears completely, you did choose an unsupported directive, for example "%e" on Windows, which will give the day of the month without leading zero on Linux.