Nintendo will perform 'emergency maintenance' to its online services on January 28 and 29.
The maintenance will affect a number of Nintendo Network functions including the online Wii U and 3DS eShops, the DSi Shop and Wii Shopping Channel.
The outages will also affect network services for Pokemon Black and White 1 and 2, and ranking/matchmaking functionality for Warriors Orochi 3 Hyper on Wii U. The full maintenance schedule is here.
"During the emergency maintenance, parts of the affected services may be intermittently unavailable," said Nintendo.
The nature of the 'emergency' went undisclosed.