One of the fun(?) things about tracking Ray Bradbury's publication history is trying to find out more about some of the more obscure periodicals that carried his work.
The short story "Time Intervening" was originally published in 1947 as "Interim". Confusingly, Bradbury used this same original title for a completely unrelated story in his first book Dark Carnival.
"Time Intervening"/"Interim" first appeared not in some pulp monthly, nor in a slick quarterly, but in something more scholarly. Epoch: a Quarterly of Contemporary Literature is a literary journal published by Cornell University. Its first issue, in fall 1947, featured not only this Bradbury short, but work by John Ciardi and e.e. cummings (the latter appearing with uncharacteristic upper-case initials).
Six years later, in Winter 1953, another Bradbury piece made its first appearance in Epoch: "The Golden Kite, the Silver Wind", better known today as one of the tales in The Golden Apples of the Sun.
Epoch is still running today. In 2009, another Cornell quarterly, Ezra, carried this article about Epoch's history.