Your 100+ hours in Breath of the Wild are safe.
The first year anniversary of the Nintendo Switch marked one year since Nintendo began its comeback to relevance and profitability, but it also marked a much more curious occasion- that when the Switch Activity Log, which tracks your play time for games you play, began to glitch for users around the world.
Put simply, it seemed that any game played more than one year ago on the Switch was having its play time reset- which meant millions of players across the world had their time for Breath of the Wild go down from hundreds of hours to zero again. Which kind of hurts, when you put that kind of time into a game, you know.
Thankfully, it seems like it was just a glitch- basically, it seems the Switch is not accounting for the year when displaying the play time, and thinks that the player only started playing the game a day ago, for example, instead of a year and a day ago (the Switch will not display the play time for any game for the first ten days that you play it).
The data is still there and being recorded- it is just not being displayed properly. Nintendo has confirmed that the data isn’t lost, and that it will be addressing this problem in a future update. So… I guess stop worrying that you won’t have anything to show for the hundreds of hours you put into Zelda.
Some Nintendo Switch owners’ play activity info is displaying incorrectly, but play activity is still being recorded accurately in the background. A future system update will resolve this issue & ensure play time data is correctly displayed. We apologize for the inconvenience.
— Nintendo of America (@NintendoAmerica) March 5, 2018