Определить период

...

How many working days in year 1918?

Here is the detail of the calculation:

Because 1918 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 8 public holidays that do not fall during a weekend and we obtain 253 working days in 1918.

Here is the list of these 8 public holidays:

1. New Year's Day : вторник, 1 январь, 1918
2. Good Friday : пятница, 29 март, 1918
3. Spring Day : среда, 1 май, 1918
4. Midsummer Day : понедельник, 24 июнь, 1918
5. Independence Restoration Day : вторник, 20 август, 1918
6. Christmas Eve : вторник, 24 декабрь, 1918
7. Christmas Day : среда, 25 декабрь, 1918
8. Second Day of Christmas : четверг, 26 декабрь, 1918

And here are the 4 public holidays falling on a weekend:

1. Independence Day : воскресенье, 24 февраль, 1918
2. Easter : воскресенье, 31 март, 1918
3. Pentecost : воскресенье, 19 май, 1918
4. Victory Day : воскресенье, 23 июнь, 1918