postdoc = [
    {"key": "something0", "start_time": datetime(2012, 1, 1), "end_time": datetime(2012, 1, 1)},
    {"key": "something1", "start_time": datetime(2012, 1, 1), "end_time": datetime(2012, 1, 1)},
    {"key": "something2", "start_time": datetime(2012, 1, 1), "end_time": datetime(2012, 1, 1)},
    {"key": "something3", "start_time": datetime(2012, 1, 1), "end_time": datetime(2012, 1, 1)},

]

experience = [
    {"key": "something0", "start_time": datetime(2012, 2, 1), "end_time": datetime(2012, 1, 1)},
    {"key": "something1", "start_time": datetime(2012, 3, 1), "end_time": datetime(2012, 1, 1)},
    {"key": "something2", "start_time": datetime(2012, 4, 1), "end_time": datetime(2012, 1, 1)},
    {"key": "something3", "start_time": datetime(2011, 1, 1), "end_time": datetime(2012, 1, 1)},
]

postdoc_end = {}
for p in postdoc:
    postdoc_end[p["key"]] = p["end_time"]

relevant_experiences = []
for e in experience:
    if e["key"] in postdoc_end and e["start_time"] > postdoc_end[e["key"]]:
        relevant_experiences.append(e)