Doraemon Movie 36: Shin Nobita no Nippon Tanjou

Tired of life at home, Nobita, Doraemon, Shizuka, Gian, and Suneo escape farther than any runaway children ever could: 70,000 years into the past, when Japan is untouched by civilization. With nobody around to stop them, they build a private paradise and enjoy complete freedom before eventually returning to the present.

Their adventure is not over. A boy named Kukuru suddenly appears in their era after being displaced through time, bringing news that his Hikari Tribe has been attacked and abducted by the Kurayami Tribe under the mysterious Gigazombie. Doraemon and his friends head back into prehistory, where rescuing Kukuru's people means confronting an enemy who understands time far better than they expected.