There must be another precedent, but there is Borges’ story, “The Other”, for the notion of a meeting between past and present in the same person. The dramatic instrumentality of Gallagher’s screenplay makes it a matter of necessity, or anyway of some importance, that the meeting take place. No doubt, this has been all but overlooked by the critical establishment (a critic always makes thirteen at table, but who cares for superstition?), such as it is.
The cunning structure accounts for that, mercifully, with its images of doubles, because the exposition is not in the dialogue but in the images. A festive gathering, a watchful wife. Rita Moreno carries this on a critical eye toward a wayward husband or a serviceable mirror.
The other instrument is a blue moon wished upon by the girlfriend and the wife forty years apart on the same night in the Catskills. The wish is granted, both couples meet in a cabin.
There is a comedy in all this, briefly played by Ben Gazzara and Moreno before a pair of flashback scenes, his early view of her parents and family, hers of his. The distance and accommodation of these two views is a correct accounting, because each gives the perspective of the reminiscer.
Gazzara gives the centerpiece in a flashback to still earlier times, and here is where Borges is transmuted into visceral imagery. Remembering an oppressive father, the young man delays marriage, and is told how happily that works.
Well enough, in the final scenes on a bridge in Paris, for that view of the Arc de Triomphe.