Define a period

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How many working days in year 1980?

Here is the detail of the calculation:

Because 1980 is a leap year, it has 366 days.

Let's remove 52 saturdays and 52 sundays. It remains 262 days.

Now, let's remove 9 public holidays that do not fall during a weekend and we obtain 253 working days in 1980.

Here is the list of these 9 public holidays:

1. Første nyttårsdag : Tuesday, 1 January, 1980
2. Skjærtorsdag : Thursday, 3 April, 1980
3. Langfredag : Friday, 4 April, 1980
4. Andre påskedag : Monday, 7 April, 1980
5. Første mai : Thursday, 1 May, 1980
6. Kristi Himmelfartsdag : Thursday, 15 May, 1980
7. Andre pinsedag : Monday, 26 May, 1980
8. Første Juledag : Thursday, 25 December, 1980
9. Andre Juledag : Friday, 26 December, 1980

And here are the 3 public holidays falling on a weekend:

1. Første påskedag : Sunday, 6 April, 1980
2. Grunnlovsdagen : Saturday, 17 May, 1980
3. Første pinsedag : Sunday, 25 May, 1980