Doraemon: Obaachan no Omoide

Doraemon: A Grandmother's Recollections

ドラえもん おばあちゃんの思い出

Nobita misses his granny that died a few years ago, so Doraemon takes Nobita to the past to see his grandmother one more time. But they face through a lot of things such as the younger selves of Nobita and his friends, and young Nobita's mother that doesn't recognize Nobita or Doraemon.

(Source: Wikipedia)