The following code contains two options; the first one doesn't use any special symbol, simply adds /time(incr.) to the column header to indicate an increasing time sequence order. The second one is a TikZ based solution:
\documentclass{article}
\usepackage{booktabs}
\usepackage{tikz}
\usetikzlibrary{calc}
\newcommand\tikzmark[1]{%
\tikz[overlay,remember picture] \coordinate (#1);}
\begin{document}
\noindent\begin{tabular}{lc}
\toprule
head1 & data/time(incr.) \\
\midrule
text & 3 \\
text & 2 \\
text & 1 \\
\bottomrule
\end{tabular}
\vspace{1cm}
\noindent\begin{tabular}{lc}
\toprule
head1 & data \\
\midrule
text & 3\tikzmark{start}\\
text & 2 \\
text & 1\tikzmark{end} \\
\bottomrule
\end{tabular}
\begin{tikzpicture}[overlay,remember picture]
\draw[->] let \p1=(start), \p2=(end) in ($(\x1,\y1)+(0.8,0.2)$) -- node[label=right:time] {} ($(\x1,\y2)+(0.8,0)$);
\end{tikzpicture}
\end{document}

\tikzmarksolution as shown in the other answer as that would be a lot more flexible. – Peter Grill Oct 22 '20 at 16:51