Define a period

...

How many working days in year 1987?

Here is the detail of the calculation:

Because 1987 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 9 public holidays that do not fall during a weekend and we obtain 252 working days in 1987.

Here is the list of these 9 public holidays:

1. Uusaasta : Thursday, 1 January, 1987
2. Iseseisvuspäev : Tuesday, 24 February, 1987
3. Suur Reede : Friday, 17 April, 1987
4. Kevadpüha : Friday, 1 May, 1987
5. Võidupüha : Tuesday, 23 June, 1987
6. Jaanipäev : Wednesday, 24 June, 1987
7. Taasiseseisvumispäev : Thursday, 20 August, 1987
8. Jõululaupäev : Thursday, 24 December, 1987
9. Esimene jõulupüha : Friday, 25 December, 1987

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

1. Ülestõusmispühad : Sunday, 19 April, 1987
2. Nelipühad : Sunday, 7 June, 1987
3. Teine jõulupüha : Saturday, 26 December, 1987