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Product in calendar (Posted on 2024-05-27) Difficulty: 3 of 5
February 13, 1976 was an interesting date. The product of the month, day, and 2-digit year is equal to the 4-digit year:

2*13*76=1976.

Find all dates in the 20th and 21st centuries with this property.

No Solution Yet Submitted by Jer    
Rating: 4.0000 (1 votes)

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Solution Computer solution | Comment 1 of 3
I found 21 such dates:

January 21, 1995: 1*21*95 = 1995
January 26, 1976: 1*26*76 = 1976
January 26, 2080: 1*26*80 = 2080
February 13, 1976: 2*13*76 = 1976
February 13, 2080: 2*13*80 = 2080
March 7, 1995: 3*7*95 = 1995
March 13, 1950: 3*13*50 = 1950
March 17, 1938: 3*17*38 = 1938
March 17, 2040: 3*17*40 = 2040
March 27, 2025: 3*27*25 = 2025
April 24, 1920: 4*24*20 = 1920
June 16, 1920: 6*16*20 = 1920
June 21, 2016: 6*21*16 = 2016
July 3, 1995: 7*3*95 = 1995
July 11, 1925: 7*11*25 = 1925
July 18, 2016: 7*18*16 = 2016
August 12, 1920: 8*12*20 = 1920
September 9, 2025: 9*9*25 = 2025
September 14, 2016: 9*14*16 = 2016
November 7, 1925: 11*7*25 = 1925
December 8, 1920: 12*8*20 = 1920

The next time this will occur is March 27, 2025.

I did not check for illegal dates such as February 31, but fortuitously, the largest day value the program found was 26.  

------------
month_names = ['',
               'January',
               'February',
               'March',
               'April',
               'May',
               'June',
               'July',
               'August',
               'September',
               'October',
               'November',
               'December']
dates = []
for month in range(1,13):
    for day in range(1,32):
        prod = month * day
        for year in range(1901,2100):
            if year == 2000:
                continue
            if prod == year / (year%100):
                dates.append('{} {}, {}: {}*{}*{} = {}'.format(month_names[month],
                                                               day, 
                                                               year, 
                                                               month, 
                                                               day, 
                                                               year%100, 
                                                               month*day*(year%100)))

for d in dates:
    print(d)

  Posted by Larry on 2024-05-27 09:30:55
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