Define a period

...

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 10 public holidays that do not fall during a weekend and we obtain 251 working days in 1991.

Here is the list of these 10 public holidays:

1. Første nyttårsdag : Tuesday, 1 January, 1991
2. Skjærtorsdag : Thursday, 28 March, 1991
3. Langfredag : Friday, 29 March, 1991
4. Andre påskedag : Monday, 1 April, 1991
5. Første mai : Wednesday, 1 May, 1991
6. Kristi Himmelfartsdag : Thursday, 9 May, 1991
7. Grunnlovsdagen : Friday, 17 May, 1991
8. Andre pinsedag : Monday, 20 May, 1991
9. Første Juledag : Wednesday, 25 December, 1991
10. Andre Juledag : Thursday, 26 December, 1991

And here are the 2 public holidays falling on a weekend:

1. Første påskedag : Sunday, 31 March, 1991
2. Første pinsedag : Sunday, 19 May, 1991