dates and τ

dates_and_frequencies.py

from datetime import  datetime, timedelta

get_random_datetime = lambda: datetime.now() - timedelta(days=random.randrange(1, 365*2), seconds=random.randrange(0, timedelta.max.seconds))
dates = [get_random_datetime() for d in range(10)]
half_year_ago = datetime.now() - timedelta(days=365/2)
dates_within_last_six_months = filter(lambda date: date >= half_year_ago, dates)

deltas = []
for index, date in enumerate(sorted(dates_within_last_six_months)):
    if index < len(dates_within_last_six_months) - 1:
        deltas.append(dates_within_last_six_months[index + 1] - dates_within_last_six_months[index])