Определить период

...

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 10 public holidays that do not fall during a weekend and we obtain 252 working days in 1980.

Here is the list of these 10 public holidays:

1. Restoration Day of the Independent Czech State : вторник, 1 январь, 1980
2. Good Friday : пятница, 4 апрель, 1980
3. Easter Monday : понедельник, 7 апрель, 1980
4. Labour Day : четверг, 1 май, 1980
5. Liberation Day : четверг, 8 май, 1980
6. Independence Day : вторник, 28 октябрь, 1980
7. Freedom and Democracy Day : понедельник, 17 ноябрь, 1980
8. Christmas Eve : среда, 24 декабрь, 1980
9. Christmas Day : четверг, 25 декабрь, 1980
10. St. Stephen's Day : пятница, 26 декабрь, 1980

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

1. St Cyril and Methodius' Day : суббота, 5 июль, 1980
2. Jan Hus Day : воскресенье, 6 июль, 1980
3. St Wenceslas Day : воскресенье, 28 сентябрь, 1980