First of all, if you're timeline is less than 10,000 years, this program could be useful.
My world is high fantasy, so my timeline is the entire 24,000 year history of time. Because of this, I've been using this format in a Google doc:
This isn't optimal for visualization, but it does keep everything in order and allows me to control+F search to find a particular event, date, year, or era.
I use a program cleverly called... wait for it... Timeline.
It's an amazing program because it makes it very easy to organize it all.
You can create multiple categories (for example: wars, special days/events, battles, elections, etc) and then view or hide them.
You could use colors on events and the background of the timeline (!) to make it even more organized.
You can add additional information and images when clicking on an event.
It supports custom dates and supports searching. As far as I know it doesn't have an end date.
I use the Timeline Project. It's pretty great and does exactly what I want.
You can set dates, but also set periods. Add pictures into the description, so when you hover over it you can see that picture. Also, you can add hyperlinks in the description, maybe you can link it to your textfiles too but I'm not sure on that.
EDIT: They are still updating it now and then, so if you encounter any problems or bugs I'm pretty sure the devs can help you out.
Yes ! It's "Timeline"... http://thetimelineproj.sourceforge.net/index.html here is a link to the site where you can get it, its free, very easy to use and under general public licence, and its the only one that fatisfy me but its a bit limited and if someone have a good alternative it can be great !
It's not a book on world building, but some people recommend that you keep a timeline.
Each one has it's way of doing things, but I would recommend Timeline for that. It's a very simple opensource program that you do can learn in minutes.
It works really well on all scales (from minutes to centuries).
First time I've seen that Timeline Project. Looks halfway decent. I had checked out Aeon Timeline and wasn't too impressed with it. Plus, $50 just for some timeline software? Nah. I'm slick. I have all that in Campfire Pro now so I'm good to go but I probably would have checked out TP if I would have known about it. Good look for anyone else that may be looking.
I use Photoshop and Illustrator for mapping purposes. Those aren't free, though...
Mediawiki for my own personal Wikipedia. It's the same software used by Wikipedia and it's freeeee. You can set it up so it works offline. Literally every tool that Wikipedia uses, you can use. Lot's of plugins as well that you can download. I sometimes have to look up how to do things, like creating a wikibox, but it's pretty easy following tutorials or copying templates. Highly recommend this one.
I also use Microsoft Word for writing. Great to write actual stories in. I'm also busy writing my own 'law book', about what things are and aren't allowed in my world. This to ensure maximum consistency.
The Timeline Project for timelines. It's also freeee!
http://thetimelineproj.sourceforge.net/screenshots.html
I've used this for timelines that span thousands of years. It's super clean, easy to use, with color coding, time periods and event description. Sounds much like what you need.
The fancy paid one is Aeon Timeline. It's geared towards fiction, so you can create custom calendars. It's pretty slick.
I think the best of the open-source alternatives is TimeLines. It only supports the modern date system and the UI is a bit clunky, but if you can shoehorn your game world's calendar into our system it works.
That project's been stalled for awhile, but the program I've been using is availible here. I think I might try to make some more progress on that now...
Aeon Timeline looks great, but since it's not compatible with Linux I use "Timeline". It doesn't integrate with Scrivener (which I use extensively), which I'd really like, but it's simple and it works.
For notes, I use TiddlyWiki, which is a Wikipedia-like program that runs in your browser. I haven't tried synchronising it across devices, though.
This is the best thing I've been able to find, it's pretty limited but it does let you have multiple things going on at once.
When that doesn't work, I've just had to resort to spreadsheets, which isn't great but it does the job, and you can have as many columns as you want.
The Timeline Project is completely free, but it does not support custom calendars. There is a calendar which is just numbers, so that's what I use.
Photoshop and Illustrator for mapmaking (not free)
The Timeline Project for timelining (free!)
Mediawiki for my wiki, it's the same software Wikipedia uses (free!)
Microsoft Words to write my own personal guides/guidelines/rules/logic (free for me, not sure if for thee)
I have written a lot of resources for myself. How to name things, where to place cities, what rules to follow, what's allowed in my world and what is not, which genre do I limit myself to? These things help a lot. Writing a guide about something is more educational than reading one.
Besides that, I use Sims to create characters to get a visual idea of how (human) characters look. I use Crusader Kings 2 for ideas about governments/marriages/trying things out. I draw sketches on paper for architecture ideas, and sometimes built a small things in Minecraft to get a 'feel'. For mapping I used World Machine, to create a heightmap that looks eroded and weathered.
Besides that, reading a lot. On the internet, in (fantasy/fiction) books, in my schoolbooks (I study law), history books, etc.
The great thing about worldbuilding is that you can take inspiration and ideas from nearly everywhere, and nearly any tool can be used. But your mind is the most important tool. Train getting ideas, train getting flow in your work, train yourself in writing better, train yourself in thinking logically when writing worlds. All these tools mean nothing if you don't train your brain.
I use yWriter with cloudsync. Free for Windows (and Mac), the Android app is about 5 €. Has the big advantage that it stores files as .rtf, so I can work on them on my Linux machine (or anywhere I don't have the software installed) as well.
For projects with huge worldbuilding and research, nothing beats a Wiki.
For timelines I use this.
I use the Timeline Project. Great piece of free software. You don't need to be online to use it and the files are saved locally. You can add links, pictures, colors, containers, etc...
I've got two monitors. On my right monitor I've got my worldmap (made in photoshop), with timeline software open too. On my left monitor I've got my mediawiki open ('create your own wikipedia' basically) where I write all of the lore ideas in my head.
If a country goes to war with another country I can update the worldmap and timeline. If a city is settled I can note it on my map. If I want to know when something happened, I look at the timeline. If I want ideas for what's next I look at the map and timeline and think what would happen next.
I like writing about wars, politics, trade, basically everything you would find in a history book. If I need inspiration I watch a documentary or visit some history subs. Playing Civilization and Crusader Kings 2 (or any paradox game for that matter) helps a LOT too.
Posted this before, but I use Timeline software, and just use arbitary dates for the events. However, you can't define what a year/month/day/hour is. It's good for planning in the millenia or minute and both at the same time, depending on what you want to do. There are different colours and all sorts. Not sure if this is the same as what you want, but I highly recommend it! :D