As far as I know, it must have been well over 200 million years ago... Finland never had any volcanoes.
Scandinavia and Finland are very ancient continental crust. Any volcanic activity was half a billion to even a billion years old. There's some old, 400 million years old volcanic traces about 50 miles or so from me. Not much to think about, but, worth noting as a reference in regard to Earth's past. It's something I think about when I'm driving and go through one of those road cuts thru bedrock and observe traces of basaltic dikes (ancient magma intrusions) in the host rock.
There's an area in Russia called the "Siberian Traps", it was the scene of huge outpourings of Lava, something called Flood Basalts. Lava just erupted and covered thousands of square kilometers to a depth of 1-3 kilometers over many millenia. Possibly resulting in the Permian Great extinction event. It's one of the largest flood basalt regions known on earth. For perspective, a single siberian trap eruption would have made Hawaii's current 20+ year eruption look miniscule.
There'll be a test on this next week. <end little professor mode>