The number of days shown are the number of days since March 3rd, 2017, the day the Nintendo Switch was released. It took Nintendo 1318 days to add themes to the 3DS, adding themes to the Switch is now way overdue.
October 2nd 2026 is gonna be an interesting one. We will hit 3,500 days, hit the 500th week, hit 2,500 business days and 1,000 weekend days all at once!