\usepackage{fancyhdr}
\usepackage{fontspec}
\usepackage{titlesec}
\usepackage{graphicx}

\usepackage{datetime}
\usepackage[iso,english]{isodate}

% http://tex.stackexchange.com/questions/246174/dynamic-title-size-using-titlesec
\newcommand{\resizetitle}[1]{\resizebox{\sectionwidth}{!}{#1}}
\newlength{\sectionwidth}
\AtBeginDocument{%
  \setlength{\sectionwidth}{0.7\textwidth}%
}

% unix shell date
%\immediate\write18{date >\jobname.date}

% no page numbers
\pagenumbering{gobble}

\setmainfont{Quattrocento Sans}
%\newfontfamily\sectionfont{Share-ItalicOSF}
%\newfontfamily\sectionfont{Josefin Slab}
%\newfontfamily\sectionfont{Roboto Light}
\newfontfamily\sectionfont{Lobster Two}

\pagestyle{fancy}
\fancyhf{}
%\rhead{various \XeTeX}
\lhead{Quattrocento Sans / Lobster Two}
\rfoot{\sectionfont\tiny{printed: \isodate{\today} \currenttime \selectfont}}

%\titleformat*{\subsection}{\sectionfont\fontsize{32}{20}\selectfont}
%\titleformat*{\subsubsection}{\sectionfont\fontsize{32}{12}\selectfont}

\titleformat{\subsubsection}
 {\Large\bfseries}
 {\thesection}
 {1em}
 {\resizetitle}

\titleformat{\subsection}
 {\Large\bfseries}
 {\thesection}
 {1em}
 {\resizetitle}