from datetime import datetime, timedelta

HALF_HOUR = timedelta(minutes=30)
ONE_DAY = timedelta(days=1)


def task(t):
    l = list()
    for el in t:
        l.append(datetime.strptime(el, '%Y-%m-%d %H:%M:%S'))

    days = set()
    for i, r in enumerate(l):
        date = r.date()
        if i == 0:
            days.add(date)
            sessions = 1
        else:
            if date in days or date - ONE_DAY in days:
                time_diff = r - l[i - 1]
                if time_diff > HALF_HOUR:
                    days.add(date)
                    sessions += 1
            else:
                days.clear()
                days.add(date)
                sessions = 1

    return len(days) >= 3 and sessions >= 6


A = ['2017-03-10 08:13:11', '2017-03-10 19:01:27', '2017-03-11 07:35:55', '2017-03-11 16:15:11', '2017-03-12 08:01:41',
     '2017-03-12 17:19:08']

B = ['2017-03-10 18:58:11', '2017-03-10 19:01:27', '2017-03-11 07:35:55', '2017-03-11 16:15:11', '2017-03-12 08:01:41',
     '2017-03-12 17:19:08']

C = ['2017-03-08 17:11:13', '2017-03-11 17:22:47', '2017-03-11 19:23:51', '2017-03-11 22:03:12', '2017-03-12 08:32:04',
     '2017-03-12 13:19:08', '2017-03-12 17:19:08']

print(task(A))
print(task(B))
print(task(C))