Define a period

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How many working days in year 1972?

Here is the detail of the calculation:

Because 1972 is a leap year, it has 366 days.

Let's remove 53 saturdays and 53 sundays. It remains 260 days.

Now, let's remove 12 public holidays that do not fall during a weekend and we obtain 248 working days in 1972.

Here is the list of these 12 public holidays:

1. New Year's Day (observance) : Monday, 3 January, 1972
2. Coming of Age Day : Monday, 10 January, 1972
3. Foundation Day : Friday, 11 February, 1972
4. Vernal Equinox Day : Monday, 20 March, 1972
5. Constitution Memorial Day : Wednesday, 3 May, 1972
6. Greenery Day : Thursday, 4 May, 1972
7. Children's Day : Friday, 5 May, 1972
8. Marine Day : Monday, 17 July, 1972
9. Respect-for-Aged Day : Monday, 18 September, 1972
10. Health and Sports Day : Monday, 9 October, 1972
11. Culture Day : Friday, 3 November, 1972
12. Labor Thanksgiving Day : Thursday, 23 November, 1972

And here are the 4 public holidays falling on a weekend:

1. New Year's Day : Saturday, 1 January, 1972
2. Shōwa Day : Saturday, 29 April, 1972
3. Autumnal Equinox Day : Saturday, 23 September, 1972
4. Emperor's Birthday : Saturday, 23 December, 1972