Define a period

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How many working days in year 1979?

Here is the detail of the calculation:

Because 1979 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 1979.

Here is the list of these 13 public holidays:

1. New Year's Day : Monday, 1 January, 1979
2. Coming of Age Day : Monday, 8 January, 1979
3. Foundation Day (observance) : Monday, 12 February, 1979
4. Vernal Equinox Day : Tuesday, 20 March, 1979
5. Shōwa Day (observance) : Monday, 30 April, 1979
6. Constitution Memorial Day : Thursday, 3 May, 1979
7. Greenery Day : Friday, 4 May, 1979
8. Marine Day : Monday, 16 July, 1979
9. Respect-for-Aged Day : Monday, 17 September, 1979
10. Autumnal Equinox Day (observance) : Monday, 24 September, 1979
11. Health and Sports Day : Monday, 8 October, 1979
12. Labor Thanksgiving Day : Friday, 23 November, 1979
13. Emperor's Birthday (observance) : Monday, 24 December, 1979

And here are the 6 public holidays falling on a weekend:

1. Foundation Day : Sunday, 11 February, 1979
2. Shōwa Day : Sunday, 29 April, 1979
3. Children's Day : Saturday, 5 May, 1979
4. Autumnal Equinox Day : Sunday, 23 September, 1979
5. Culture Day : Saturday, 3 November, 1979
6. Emperor's Birthday : Sunday, 23 December, 1979