"Ev'ry Time We Say Goodbye" is a song by Cole Porter, introduced in 1944 in the musical revue, Seven Lively Arts. The song became a jazz standard, recorded by Ella Fitzgerald, as well as John Coltrane.
As well as being a very pretty song, Porter adds a little cleverness; as the lyrics say "major to minor," the tune changes from major to minor chords.
In addition to the great interpretations listed above, I also quite like the version Oscar Peterson recorded for Oscar Peterson Plays The Cole Porter Songbook (1959). Here is just a bit of that one. And here, Ella Fitzgerald's version underscores the parting of Snoopy and Charlie Brown. Good grief: