The next Nintendo Switch firmware update has been announced, and it will go live on September 18, 2018, the same day Nintendo Switch Online launches. The company says that it will happen at 5pm PT/7pm CT/8pm ET on its official support website.
In addition, Nintendo Switch eShop maintenance has been announced. From 5pm-8pm PT/7pm-10pm CT/8pm-11pm ET, people will not be able to access the eShop. After maintenance, Nintendo Switch Online subscriptions can be purchased.
As an important aside, Nintendo Accounts will be permanently linked to Nintendo Switch user accounts after the Nintendo Switch firmware update. The support site says people have until 5pm PT/7pm CT/8pm ET on September 18, 2018 to unlink an account ahead of the firmware update. After the update, it can not be changed.
Nintendo Switch Online launches on September 18, 2018.