Please see if this meets the requirement
The options have been listed and not in continuous line for better readability
Please revert for additional query

\documentclass[10pt]{article}
\usepackage[utf8]{inputenc}
\usepackage{chronosys}
\usepackage[paperwidth=34cm, paperheight=10cm]{geometry}%taille du document
\definecolor{blue}{HTML}{84CECC}
\definecolor{gr}{HTML}{375D81}
%
%
%
\begin{document}
%---------------------timeline----------------%
\startchronology[
align=left,
startyear=1999,
stopyear=2016,
height=0pt,
startdate=false,
stopdate=false,
dateselevation=0pt,
arrow=false,
box=true
]
%
\chronograduation[event][dateselevation=0pt]{1}
%---------------------periods----------------%
\chronoperiode[
textstyle=\raggedleft\colorbox{gr!50},
color=gr,
startdate=false,
bottomdepth=0pt,
topheight=8pt,
textdepth=-25pt,
dateselevation=16pt,
stopdate=false
]
{2005}{2010}{University of Tennessee Chattanooga}
%
\chronoperiode[
textstyle=\colorbox{blue!50},
color=blue,
startdate=false,
bottomdepth=8pt,
topheight=16pt,
textdepth=-25pt,
dateselevation=12pt,
stopdate=false
]
{2011}{2015}{Tennesse Technological University}
%
\stopchronology
\end{document}