https://www.gamespot.com/articles/nintendo-switch-is-resetting-play-times-after-one-/1100-6457122/

The Nintendo Switch is already celebrating its first anniversary in parts of the world, but some Switch owners are discovering an unpleasant surprise on the console's birthday. It appears the Switch only keeps track of your game play times for one year and has begun resetting many players' records.

As pointed out in a thread on video game forum ResetEra, play times for launch day titles are being reset on Switch profiles. GameSpot has verified the issue; as you can see in the screenshot below, our Switch now says that we first started playing The Legend of Zelda: Breath of the Wild nine days ago.