Board Thread:Questions and Answers/@comment-32022228-20171207084025/@comment-32182236-20171209132056

Several centuries-Likely somewhere between 400-1700 years.

Undertale takes place in the present day, in the 2010s.

The War takes place in either the medieval era or the Roman Era. Somewhere between around 100BC and 1550AD.

Eight humans fell underground. Seven between the War and Frisk. This places Chara's likely fall around 1/8th of the way between the War and Frisk.