I already have 2 libraries, compatible with arduino in source code, but their names are like this:
atmega-timers
atmega-scheduler
Arduino gave me an error saying that libraries can't contain signs and such. Why exists such a limitation? I'm not using spaces or numbers.
You need to post a screen shot of the library directory listing and the EXACT error message.
The - is a sign (like + or -). It may not be a valid character in a file name. Valid characters may be platform dependent, too, so mentioning what OS you are using would be useful.
When I was just starting my Arduino hobby I used to name file names like haha-01 but arduino ide changes it to haha_01, with the underscore. I suspect it comes from the fact that arduino ide is a hacked version of Processing ide, which also does this naming convention, possibly to avoid any problems across OS.