Which comes first chronologically, Jessica Jones Season 1 or Daredevil Session 2?

As far as we can tell, the Netflix shows are taking place in the same order they air, but several months "behind" real-time.

The shows are extremely vague on their timelines, but Jessica Jones appears to take place sometime in January or February of 2015, based on their description of the January 2014 accident as "a year ago", which puts it just prior to the events of Age of Ultron. Daredevil Season 2 appears to take place starting in either late August or early September of 2015, based on the unexpected heat wave, but clearly ends on Christmas that year. So Daredevil starts roughly 6 months after Jessica Jones ends.

Note that there are at least 3 references/callbacks to Jessica Jones in Daredevil season 2: the nurse makes a reference to Luke Cage being hard to injure, Foggy's girlfriend makes a reference to Jessica Jones being a powered person, and Hogarth shows up at the end to hire Foggy. None of those necessarily mean that Jessica Jones came first but they strongly imply it; especially since both Jessica and Luke were trying very hard to hide their powers before the events of that show.