On 16-12-20, Maarten sent me as message asking whether I knew what was special about today's date. I didn't know, but it turned out that 12^2+16^2=20^2. So I made a little Python program to check this for all years from 2000-3000:

check.py

for y in range(0, 1000):
    for m in range(1,13):
        max_day = 32

        # Month length correction
        if m == 11 or m == 9 or m == 6 or m == 4:
            max_day = 31
        # Leap year correction
        elif m == 2:
            y_actual = y + 2000

            max_day = 29

            if (y_actual % 4) == 0:
                if (y_actual % 100) == 0:
                    if (y_actual % 400) == 0:
                        max_day = 30
                else:
                    max_day = 30

        for d in range(1,max_day):
            if y ** 2 + m ** 2 == d ** 2:
                print("y**2 + m**2 = d**2, for: " + str(d) + "-" + str(m) + "-" + str(y+2000))
            if d ** 2 + m ** 2 == y ** 2:
                print("d**2 + m**2 = y**2, for: " + str(d) + "-" + str(m) + "-" + str(y+2000))
            if y ** 2 + d ** 2 == m ** 2:
                print("y**2 + d**2 = m**2, for: " + str(d) + "-" + str(m) + "-" + str(y+2000))