I am currently writing a short story, and I am considering using two different first-person narrators in two different timelines. The two timelines will be clearly marked by headings stating the date and locations of the scenes in question. However, there is a risk that the reader will see "I" in both sections and assume that both narrators/characters are the same person unless I clarify the matter very carefully when introducing them.
I am looking for tips on doing this effectively. Has anyone tried this before? How can I prevent confusion tween the two narrators?