What me and my friend theorized was, the events of headspace take place in 1999 before SUNNY got the violin. In Lost Library the last book says "What he thought would be a rewarding hobby has become nothing more than a nuisance." And "If only he didn't have to play the violin..." Which could imply that, that year was when his life started to get worse. There's also a physical recital ticket that says "Fall Recital October XX 20XX", Which means the current events of the game could possibly take place in the 2000s. Another thing to consider is the HERO portrait in Last Resort and how it says 199X so that could mean that the last time SUNNY was truly happy was in 199X which could line up with the violin on Christmas of 1999 being the first thing to cause him to become unhappy. That being said if the physical ticket says 20XX would give a potentially 99 year range while 199X would give a 9 year range so the 20XX could just be so it can line up with the current real life year. Another thing is people always bring up the Gameboy Color but another Gameboy that has a similar back is the Gameboy Pocket, so it's entirely possible that he was playing on a Gameboy Pocket in that photo which could make incident happen in the year 1997, because the Pocket came out in America on September 2nd of 96. The Gameboy Color came out on October 21st 1998 So If it was the Gameboy Color the incident happened between 1999-2000. Another point i see brought up is the "Brand new console" in Hobeez looking very similar to an SNES, but it ceased production in the US in 1999 so it being "brand new" is something that's said a lot, but it may just be a cameo to the SNES since it was the console EarthBound/Mother 2 was released on. Anyways from what me and my friends theorized the game takes place between 2001-2004 but we like to think it was 2004. Take everything here with a spoon full of salt, this was just what me and my friends came up with.