why is this one line causing me problems

Because of everything :) that these links explain Re: Backtick failure in Windows 7 (common pitfall), qx/system/exec, $PATH

FWIW, you don't want to shell out to date for a timestamp, scalar gmtime, POSIX::strftime, Time::Piece... Re: error on file open, Re^2: Date plus Time sort from file ( Time::Piece->strptime/strftime example, Re: Subtracting minutes from a string ( Time::Piece->strptime )