Answer to: https://fivethirtyeight.com/features/when-will-the-arithmetic-anarchists-attack/

anarchists.py

from datetime import date, timedelta
from collections import Counter

# all the dates that fit the equation:
dates = [*filter(lambda d:d.year - 2000 == d.month * d.day, [date(2001, 1, 1) + timedelta(i) for i in range(36158)])]

# total events is number of dates:
print(len(dates))

# Counter.most_common is the year that occurs most:
print(Counter(d.year for d in dates).most_common(1)[0])

# Counter value == 1 -> years that occur least
print([*filter(lambda x: x[1] == 1, Counter(d.year for d in dates).most_common())])

# Longest period without an attack is the difference between two consequetive items:
print(max([(d2 - d1, d1, d2, ) for d1, d2 in zip(dates[:-1], dates[1:])]))