How does the use of time and tense create effect

I don’t know ‍♀️ I just From 1915 until 1946, some 25,000 pieces of paper were exchanged between two major 20th-century artists. Painter Georgia O'Keeffe and photographer Alfred Stieglitz wrote each other letters — sometimes two and three a day, some of them 40 pages long. The correspondence tracks their relationship from acquaintances to admirers to lovers to man and wife to exasperated — but still together — long-marrieds.

The first volume of those letters has just been