I have a written a timeline environment inspired by the question and answers of the following TeX.SX question: timeline and tikz

\documentclass[10pt]{article}
\usepackage[paperwidth=210mm,%
paperheight=297mm,%
tmargin=7.5mm,%
rmargin=7.5mm,%
bmargin=7.5mm,%
lmargin=7.5mm,
vscale=1,%
hscale=1]{geometry}
\usepackage[utf8]{inputenc}
\usepackage[T1]{fontenc}
\usepackage{tikz}
\usetikzlibrary{arrows, calc, decorations.markings, positioning}
\pagestyle{empty}
\makeatletter
\newenvironment{timeline}[6]{%
% #1 is startyear
% #2 is tlendyear
% #3 is yearcolumnwidth
% #4 is rulecolumnwidth
% #5 is entrycolumnwidth
% #6 is timelineheight
\newcommand{\startyear}{#1}
\newcommand{\tlendyear}{#2}
\newcommand{\yearcolumnwidth}{#3}
\newcommand{\rulecolumnwidth}{#4}
\newcommand{\entrycolumnwidth}{#5}
\newcommand{\timelineheight}{#6}
\newcommand{\templength}{}
\newcommand{\entrycounter}{0}
% https://tex.stackexchange.com/questions/85528/checking-whether-or-not-a-node-has-been-previously-defined
% https://tex.stackexchange.com/questions/37709/how-can-i-know-if-a-node-is-already-defined
\long\def\ifnodedefined##1##2##3{%
\@ifundefined{pgf@sh@ns@##1}{##3}{##2}%
}
\newcommand{\ifnodeundefined}[2]{%
\ifnodedefined{##1}{}{##2}
}
\newcommand{\drawtimeline}{%
\draw[timelinerule] (\yearcolumnwidth+5pt, 0pt) -- (\yearcolumnwidth+5pt, -\timelineheight);
\draw (\yearcolumnwidth+0pt, -10pt) -- (\yearcolumnwidth+10pt, -10pt);
\draw (\yearcolumnwidth+0pt, -\timelineheight+15pt) -- (\yearcolumnwidth+10pt, -\timelineheight+15pt);
\pgfmathsetlengthmacro{\templength}{neg(add(multiply(subtract(\startyear, \startyear), divide(subtract(\timelineheight, 25), subtract(\tlendyear, \startyear))), 10))}
\node[year] (year-\startyear) at (\yearcolumnwidth, \templength) {\startyear};
\pgfmathsetlengthmacro{\templength}{neg(add(multiply(subtract(\tlendyear, \startyear), divide(subtract(\timelineheight, 25), subtract(\tlendyear, \startyear))), 10))}
\node[year] (year-\tlendyear) at (\yearcolumnwidth, \templength) {\tlendyear};
}
\newcommand{\entry}[2]{%
% #1 is the year
% #2 is the entry text
\pgfmathtruncatemacro{\lastentrycount}{\entrycounter}
\pgfmathtruncatemacro{\entrycounter}{\entrycounter + 1}
\ifdim \lastentrycount pt > 0 pt%
\node[entry] (entry-\entrycounter) [below of=entry-\lastentrycount] {##2};
\else%
\pgfmathsetlengthmacro{\templength}{neg(add(multiply(subtract(\startyear, \startyear), divide(subtract(\timelineheight, 25), subtract(\tlendyear, \startyear))), 10))}
\node[entry] (entry-\entrycounter) at (\yearcolumnwidth+\rulecolumnwidth+10pt, \templength) {##2};
\fi
\ifnodeundefined{year-##1}{%
\pgfmathsetlengthmacro{\templength}{neg(add(multiply(subtract(##1, \startyear), divide(subtract(\timelineheight, 25), subtract(\tlendyear, \startyear))), 10))}
\draw (\yearcolumnwidth+2.5pt, \templength) -- (\yearcolumnwidth+7.5pt, \templength);
\node[year] (year-##1) at (\yearcolumnwidth, \templength) {##1};
}
\draw ($(year-##1.east)+(2.5pt, 0pt)$) -- ($(year-##1.east)+(7.5pt, 0pt)$) -- ($(entry-\entrycounter.west)-(5pt,0)$) -- (entry-\entrycounter.west);
}
\newcommand{\plainentry}[2]{% plainentry won't print date in the timeline
% #1 is the year
% #2 is the entry text
\pgfmathtruncatemacro{\lastentrycount}{\entrycounter}
\pgfmathtruncatemacro{\entrycounter}{\entrycounter + 1}
\ifdim \lastentrycount pt > 0 pt%
\node[entry] (entry-\entrycounter) [below of=entry-\lastentrycount] {##2};
\else%
\pgfmathsetlengthmacro{\templength}{neg(add(multiply(subtract(\startyear, \startyear), divide(subtract(\timelineheight, 25), subtract(\tlendyear, \startyear))), 10))}
\node[entry] (entry-\entrycounter) at (\yearcolumnwidth+\rulecolumnwidth+10pt, \templength) {##2};
\fi
\ifnodeundefined{invisible-year-##1}{%
\pgfmathsetlengthmacro{\templength}{neg(add(multiply(subtract(##1, \startyear), divide(subtract(\timelineheight, 25), subtract(\tlendyear, \startyear))), 10))}
\draw (\yearcolumnwidth+2.5pt, \templength) -- (\yearcolumnwidth+7.5pt, \templength);
\node[year] (invisible-year-##1) at (\yearcolumnwidth, \templength) {};
}
\draw ($(invisible-year-##1.east)+(2.5pt, 0pt)$) -- ($(invisible-year-##1.east)+(7.5pt, 0pt)$) -- ($(entry-\entrycounter.west)-(5pt,0)$) -- (entry-\entrycounter.west);
}
\begin{tikzpicture}
\tikzstyle{entry} = [%
align=left,%
text width=\entrycolumnwidth,%
node distance=10mm,%
anchor=west]
\tikzstyle{year} = [anchor=east]
\tikzstyle{timelinerule} = [%
draw,%
decoration={markings, mark=at position 1 with {\arrow[scale=1.5]{latex'}}},%
postaction={decorate},%
shorten >=0.4pt]
\drawtimeline
}
{
\end{tikzpicture}
\let\startyear\@undefined
\let\tlendyear\@undefined
\let\yearcolumnwidth\@undefined
\let\rulecolumnwidth\@undefined
\let\entrycolumnwidth\@undefined
\let\timelineheight\@undefined
\let\entrycounter\@undefined
\let\ifnodedefined\@undefined
\let\ifnodeundefined\@undefined
\let\drawtimeline\@undefined
\let\entry\@undefined
}
\makeatother
\begin{document}
\begin{timeline}{1900}{1990}{2cm}{2.5cm}{5cm}{12cm}
\entry{1903}{Wilbur and Orville Wright fly the first powered airplane}
\entry{1914}{Assassination of Franz Ferdinand}
\plainentry{1917}{The October Revolution}
\entry{1928}{Discovery of Penicillin}
\plainentry{1929}{Stock Market Crash of 1929}
\entry{1941}{Attack on Pearl Harbor}
\plainentry{1944}{D-Day}
\entry{1945}{The Bombing of Hiroshima}
\plainentry{1947}{Creation of Israel as a Jewish State}
\entry{1963}{US president John F. Kennedy assassinated in Dallas}
\entry{1969}{The Moon Landing}
\plainentry{1989}{Fall of the Berlin Wall}
\end{timeline}
\bigskip
Text from: A Brief History of LaTeX http://www.xent.com/FoRK-archive/feb98/0307.html
\smallskip
\begin{timeline}{1974}{1985}{2cm}{7cm}{10cm}{0.45\textheight}
\entry{1974}{Donald Knuth stops submitting papers to the AMS because ``the finished
product was just too painful for me to look at''.}
\entry{1977}{Knuth begins his research on typography.}
\entry{1978}{Knuth delivers an AMS Gibbs Lecture entitled Mathematical Typography to the AMS membership at its annual meeting.}
\entry{1979}{Digital Equipment Corporation and the AMS jointly publish Knuth's TeX and METAFONT: New Directions in Typesetting.}
\entry{1980}{The first draft of Spivak's Joy of TeX is announced in TUGboat, vol. 1, no. 1.}
\entry{1982}{Spivak announces AMS-TeX at the joint math meetings.}
\entry{1982}{Version 0 of Spivak's Joy of TeX is released.}
\entry{1982}{Knuth releases dvitype, a model DVI driver.}
\entry{1983}{Lamport writes a LaTeX manual, the earliest known LaTeX manual in existence.}
\entry{1984}{Addison-Wesley publishes Knuth's The TeXbook, destined to become the definitive TeX reference.}
\entry{1984}{Lamport releases version 2.06a of the LaTeX macros.}
\entry{1985}{The Computer Modern (CM) fonts replace the American Modern (AM) fonts in TeX.}
\entry{1985}{Patashnik releases BibTeX version 0.98 for LaTeX 2.08. [``BibTeX 1.0'', TUGboat, vol. 15, no. 3, pp. 269--274, Sept. 1994.}
\end{timeline}
\end{document}
beamer
label since the question is closely related to presentation slides.