A simple package to make horizontal timeline. Taken and heavily modified from somewhere in the internet.

chronology.sty

\NeedsTeXFormat{LaTeX2e}%
\ProvidesPackage{chronology}[2015/03/27 v1.1.1 Horizontal timeline]%
\RequirePackage{calc}%
\RequirePackage{tikz}%
\RequirePackage{xparse}%
% Defining counters and lengths
\newcounter{step}\newcounter{stepstart}\newcounter{stepstop}%
\newcounter{yearstart}\newcounter{yearstop}\newcounter{deltayears}%
\newlength{\xstart}\newlength{\xstop}%
\newlength{\unit}\newlength{\timelinewidth}%
\newlength{\ticklength}\newlength{\timelineheight}
\newsavebox{\timelinebox}%
% Defining TikZ styles for labels and events
\tikzset{%
  ,chronevent/.style={fill=black,draw=none,opacity=0.5}
  ,chronperiod/.style={fill=black,draw=none,opacity=0.5}
  ,chronlabel/.style={opacity=1}
  ,chrontickslabel/.style={scale=0.7,chronlabel}
  ,chroneventlabel/.style={chronlabel}
  ,eventlabel/.style={chroneventlabel,anchor=south west,yshift=.2\unit,rotate=45}
  ,flippedeventlabel/.style={chroneventlabel,anchor=north west,yshift=-.2\unit,rotate=-45}
  }

\makeatletter%
\newif\ifchronology@star%
\newenvironment{chronology}{%
  \@ifstar{\chronology@startrue\chronology@i*}{\chronology@starfalse\chronology@i*}%
}{%
  \end{tikzpicture}%
  \end{lrbox}%
  \resizebox{\timelinewidth}{!}{\usebox{\timelinebox}}%
}%
\def\chronology@i*{%
  \@ifnextchar[{\chronology@ii*}{\chronology@ii*[{5}]}%
}%
\def\chronology@ii*[#1]#2#3#4{%
  \@ifnextchar[{\chronology@iii*[{#1}]{#2}{#3}{#4}}{\chronology@iii*[{#1}]{#2}{#3}{#4}[{#4}]}%
}%
\def\chronology@iii*[#1]#2#3#4[#5]{%
  \newif\ifflipped%
  \ifchronology@star%
    \flippedtrue%
  \else%
    \flippedfalse%
  \fi%
  \setcounter{step}{#1}%
  \setcounter{yearstart}{#2}\setcounter{yearstop}{#3}%
  \setcounter{deltayears}{\theyearstop-\theyearstart}%
  \setlength{\unit}{#5/\thedeltayears}%
  \setlength{\timelinewidth}{#4}%
  \setlength{\ticklength}{.12\unit}%
  \setlength{\timelineheight}{.1\unit}%
  \pgfmathsetcounter{stepstart}{\theyearstart-mod(\theyearstart,\thestep)}%
  \pgfmathsetcounter{stepstop}{\theyearstop-mod(\theyearstop,\thestep)}%
  \addtocounter{step}{\thestepstart}%
  \begin{lrbox}{\timelinebox}%
    \begin{tikzpicture}[
      % For compatibity with babel. Handling of active characters in TikZ.
      handle active characters in code,
      handle active characters in nodes,
      ]
      \draw [->] (0,0) -- (\thedeltayears*\unit+\unit, 0);%
      \addtocounter{deltayears}{1}%
      \foreach \x in {\thestepstart,\thestep,...,\thestepstop}{%
        \pgfmathsetlength\xstop{(\x-\theyearstart)*\unit}%
        \draw[xshift=\xstop] (0,-\ticklength) -- (0,\ticklength);%
        \ifflipped%
          \node[chrontickslabel,above,inner sep=0pt]
          at (\xstop,\ticklength) {\x};%
        \else%
          \node[chrontickslabel,below,inner sep=0pt]
          at (\xstop,-\ticklength) {\x};%
        \fi%
      }%
}%
\makeatother%
\DeclareDocumentCommand \event {s m m}{%
  \pgfmathsetlength\xstop{(#2-\theyearstart)*\unit}%
  \IfBooleanTF{#1}{\flippedtrue}{\flippedfalse}
  \ifflipped%
    \draw[chronevent]%
    (\xstop, 0) -- (\xstop+\timelineheight/2,0)
    arc(0:-180:\timelineheight/2) -- cycle
    node[flippedeventlabel] {#3};%
  \else%
    \draw[chronevent]%
    (\xstop, 0) -- (\xstop+\timelineheight/2,0)
    arc(0:180:\timelineheight/2) -- cycle
    node[eventlabel] {#3};%
  \fi%
}
\DeclareDocumentCommand \period {s m m m}{%
  \pgfmathsetlength\xstart{(#2-\theyearstart)*\unit}%
  \pgfmathsetlength\xstop{(#3-\theyearstart)*\unit}%
  \IfBooleanTF{#1}{\flippedtrue}{\flippedfalse}
  \ifflipped%
    \draw[chronperiod,rounded corners=\timelineheight/2]%
    (\xstart,-\timelineheight) rectangle%
    node[flippedeventlabel] {#4} (\xstop,0);%
  \else%
    \draw[chronperiod,rounded corners=\timelineheight/2]%
    (\xstart,0) rectangle%
    node[eventlabel] {#4} (\xstop,\timelineheight);%
  \fi%
}
\newcommand{\decimaldate}[3]{(#1-1)/31/12+(#2-1)/12+#3}%
\endinput%

example.tex

\documentclass[aspectratio=169,dvipsnames,svgnames,10pt]{beamer}

\usepackage{tikz}
\usepackage{chronology}

\begin{document}

\begin{frame}[t]
  \noindent
  \begin{chronology}
    [2] % Granularity of the scale
    {2014} % Start
    {2020} % Stop
    {\textwidth} % External Width
    [10cm] % Internal Width, Allow to adjust the scale

    % Let's use horizontal labels at the top
    \tikzset{eventlabel/.style={chroneventlabel,text depth=0pt,yshift=.2\unit}}
    
    % A simple period
    \period{2014.2}{2014.7}{Period}
    
    % A Flipped period
    \period*{2017}{2017.3}{Period Under}

    % We can redefine the style locally
    \tikzset{chronperiod/.style={fill=RoyalBlue,fill opacity=0.8}}
    \period{2014.7}{2017.7}{\color{RoyalBlue}Blue Period}

    % An individual event
    \event{2018}{Event}
    
    % An event with custom filling, smaller label, and on the other side
    \tikzset{chronevent/.style={fill=black}}
    \tikzset{flippedeventlabel/.style={
        chroneventlabel,anchor=north west,yshift=-.2\unit,rotate=-45,scale=0.7
      }}
    \event*{2019}{Event Under}

    % We can also use overlays
    \tikzset{chronperiod/.style={fill=Red,fill opacity=0.8}}
    \visible<2>{\period{2018.7}{2019.7}{\color{Red}Period later}}
  \end{chronology}

\end{frame}

\end{document}



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Is there a way to specify the size of the event point on the line? I want it to be a little smaller if possible. I guess its "chronevent". But which property do I need to set in style to which value?

You can try to play around with \timelineheight for that. I didn't really make that more customizable.