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.
See here for Linux and for Windows
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.