Trying to identify a short story (possibly read in Asimov's SF magazine) from the late 70s. A man - possibly a professor or scientist - is working or somehow involved with a young man and young woman. I think they have some interest in either time travel or the properties of time. The professor/scientist has a device or capability that allows him to see the couple's past/present/future - basically their entire lives) at the same time.
This might be the short story "Life-Line", by Heinlein.
The story was published in Astounding Science-Fiction in 1939 and was in fact Heinlein's first published story.
Going by the ISFDB, it was never published in Asimov's, but it has been included in the 1979 collection, The Great Science Fiction Stories Volume 1, 1939, which was edited by Asimov and Greenberg, which was prominently displayed on the cover.
Professor Pinero has built a machine that can predict how long a person will live.
A young couple comes to him for a consult and he discovers they only have an hour or so left to live. Without telling them, faking a malfunction of his device instead, he tries to stall them, trying in vain to change their destiny. As the leave the building, they're hit by a car.
Life insurance companies see their profits dwindle, since people know when they will die. They sue him but lose, so they resort to more drastic measures to stop him. As it turns out, as part of an experiment to prove his machine, Pinero has predicted his own death correctly.