what is datta?
"きれいだった" what does that mean? "kirei" beautiful but "だった" why is きれい with だった ?

Question

what is datta?
"きれいだった"  what does that mean? "kirei" beautiful but "だった" why is きれい  with  だった ?

Answer

きれいだった - kirei datta: it means past situation.(Past)
きれいだ - kirei da: it means present situation.(Now)

EX: 
その女性は綺麗だった。- sono josei ha kirei datta.
The woman was beautiful.

その女性は綺麗だ。 - sono josei ha kirei da.
The woman is beautiful.