a wistful desire to return in thought or in fact to a former time in one's life, to one's home or homeland, or to one's family and friends; a sentimental yearning for the happiness of a former place or time

a nostalgia for his college days.

something that elicits or displays nostalgia.

adjective

cornball , down memory lane , drippy , homesick , like yesterday , lonesome , longing , mushy * , regretful , sappy * , sentimental , sloppy , syrupy , wistful , yearning