TBS News reports on the matter
That is a lengthy period but one that may be needed to curb the outbreak in Japan and prepare the country for next year's Olympics.
Just take note that even with the state of emergency declaration, the government cannot legally enforce citizens to stay at home but can only request that they do so.
However, such a declaration will surely see many businesses and services shut shop and that will hopefully reduce the need for people to leave their houses during the period.