Define a period

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How many working days in year 1991?

Here is the detail of the calculation:

Because 1991 is not a leap year, it has 365 days.

Let's remove 52 saturdays and 52 sundays. It remains 261 days.

Now, let's remove 13 public holidays that do not fall during a weekend and we obtain 248 working days in 1991.

Here is the list of these 13 public holidays:

1. New Year's Day : Tuesday, 1 January, 1991
2. Coming of Age Day : Monday, 14 January, 1991
3. Foundation Day : Monday, 11 February, 1991
4. Vernal Equinox Day : Wednesday, 20 March, 1991
5. Shōwa Day : Monday, 29 April, 1991
6. Constitution Memorial Day : Friday, 3 May, 1991
7. Children's Day (observance) : Monday, 6 May, 1991
8. Marine Day : Monday, 15 July, 1991
9. Respect-for-Aged Day : Monday, 16 September, 1991
10. Autumnal Equinox Day : Monday, 23 September, 1991
11. Health and Sports Day : Monday, 14 October, 1991
12. Culture Day (observance) : Monday, 4 November, 1991
13. Emperor's Birthday : Monday, 23 December, 1991

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

1. Greenery Day : Saturday, 4 May, 1991
2. Children's Day : Sunday, 5 May, 1991
3. Culture Day : Sunday, 3 November, 1991
4. Labor Thanksgiving Day : Saturday, 23 November, 1991