That depends on which patents. In the US, patents can be anywhere from 14-20 years depending on type of patent. A patent will expire early if renewal fees aren't paid, and time extensions are possible in certain circumstances that add up to three years. So basically any patents from before 1999 can be considered expired, any patents between 1999-2002 are probably expired, anything between 2002-2008 might be in effect, and anything patented after 2008 should be assumed in effect. You can check the USPTO site to be sure, but since you're in Finland you have to check whether any filed patents are effective in your area.
Not that this particularly matters if you're building something for yourself. In the US, patents can't prevent individuals from copying protected IP for private use, but again since you're not in the US it depends on your country's laws and which intellectual property treaties your country has signed.
And I swear, I've only learned and retained as much as I know about patents because of the controversy over GIF images being patent-encumbered, which was intensely relevant to my profession a couple decades ago (since if we didn't do things right UNISYS could plausibly bill our clients for superfluous thousands of dollars each due to their websites having animated GIFs that had not been produced with appropriately licensed software).
