A Tale of Lost Time (1978)

Three evil wizards from a gloomy enchanted forest littered with broken toys and school supplies enter the city through a secret door in the fence to find three lazy children who "waste time." Having found such lazy people - a schoolboy and a schoolgirl, sorcerers deceive them by deceiving them of the time that they thoughtlessly lost by skipping school. As a result, old people turn into big children, and children into little grandparents.