I'd like to provide my own answer to my question, because I actually found another way for this problem: TiKZ. I'm not sure what is the first thing that prompted me to use this package (if you think I might have took something from one of your answers, please let me know so I could attribute any external help), but I'm sure I used Box and Whisker plot from texample.net/tikz. The output is this one:

It's perfect for a timeline, but it needs some changes and from now on, I'll explain my changes and some adds to make it work. A note: There are certainly better ways to do some things I'm going to explain, if you find one, feel free to comment.
Also, this answer is going to be very long.
Setting up
First let's delete everything we don't need and let's keep the line below. If you typeset now, you'll get a line above. It's ok, we'll fill everything soon. I chose landscape but this depends on your timeline: does it consist of many years with a few events? Or only a few years with a lot of events?
\documentclass[10pt]{article}
\usepackage[a4paper, margin=1cm, landscape]{geometry}
\usepackage{rotating}
\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{arrows,backgrounds,snakes}
\begin{document}
\begin{tikzpicture}
%draw horizontal line
\draw (0,0) -- (12,0);
%draw vertical lines
\foreach \x in {0,1,2,...,12}
\draw (\x cm,3pt) -- (\x cm,-3pt);
\end{tikzpicture}
\end{document}
Drawing the dates
Note: the previous solution for this has been proven to be somewhat tedious to do, but thanks to Torbjørn T.'s help, here is a fix (automatized):
\foreach \x [evaluate=\x as \year using int(1900+\x*10)] in {0,1,...,12}{
\draw (\x,0) node[below=7pt,anchor=east,xshift=5pt,rotate=45] {$\year$};
\draw (\x cm,3pt) -- (\x cm,-3pt);}
I think the simplest/best approach is to jump every 10 years. Why? Because if we set every ten years, it will be easier to set a date. For example: if the point 5 is 1950 and 6 is 1960, then 5.5 will be 1955! It's simple, right? The number perfectly correspond to dates. While if we just every 5 years, 5 will be 1950 and 6 = 1955, so 1953 will be 5.6... Not very intuitive.
Stretching the line
If you want the line to cover all of your page, after \being{tikzpicture}, add [x=2cm], for example:

Inserting data
There are two main ways to insert data. Let's retake the first screenshot:

One is the box with the content inside, the other one is the line. I'll take inspiration from the image in the question but change something, then post the code:

Add this code after the date \foreach:
\filldraw[fill=white] (5.5, 10) rectangle (9.5, 9)
node[midway, align=center, text width=7cm]{a person};
\filldraw[fill=white] (6, 9) rectangle (12, 8)
node[midway, align=center, text width=7cm]{another person};
\filldraw[fill=white] (1, 8) rectangle (5, 7)
node[midway, align=center, text width=7cm]{yet another person};
\filldraw[fill=white] (3, 7) rectangle (7, 6)
node[midway, align=center, text width=7cm]{wow, another person again};
\draw[|-|] (4.4, 4) -- (7.4, 4) node[midway, above, align=center, text width=7cm]{Event};
\node[below] at (4.4,4) {\textsc{Start}};% label the hinge
\node[below] at (7.4,4) {\textsc{End}};% label the hinge
\draw[|-|] (0.8, 2) -- (0.9, 2) node[midway, above, align=center, text width=7cm]{Event};
A little explanation:
\filldraw[fill=white] creates a shape filled with white, (5.5, 10) rectangle (9.5, 9) decides what shape it is and it tells the coordinates in this order: (left, top) ... (right, bottom). So if you want to add more content in it, just make it taller, by writing (5.5, 12) rectangle (9.5, 8), for example.
node[midway, align=center, text width=7cm] is important. midway puts the text at the center, along with align, and text width makes it fit into the rectangle, otherwise it will go out of it.
\draw[|-|] (4.4, 4) -- (7.4, 4) draws a line from 4.4 to 7.4, at the 4th level. The [|-|] decides that style are the hinges, they could be arrows: [<->].
\node[below] at (4.4,4) {\textsc{Start}};% label the hinge, well, it's clear. The [below] can be changed to right or left, or above, of course.
Since this is a TiKZ picture, you can add arrows between rectangles, etc.
pdfganttpackage, you can design almost anything with it. It's "only" an extension of the very versatile graphics packagetikzfor making this kind of chart. – Stephan Lehmke Mar 30 '12 at 22:43