How many working days in year 1964?
Here is the detail of the calculation:
Because 1964 is a leap year, it has 366 days.
Let's remove 52 saturdays and 52 sundays. It remains 262 days.
Now, let's remove 11 public holidays that do not fall during a weekend and we obtain 251 working days in 1964.
 Here is the list of these 11 public holidays: 
 
 1. Restoration Day of the Independent Czech State : среда, 1 январь, 1964 
2. Good Friday : пятница, 27 март, 1964 
3. Easter Monday : понедельник, 30 март, 1964 
4. Labour Day : пятница, 1 май, 1964 
5. Liberation Day : пятница, 8 май, 1964 
6. Jan Hus Day : понедельник, 6 июль, 1964 
7. St Wenceslas Day : понедельник, 28 сентябрь, 1964 
8. Independence Day : среда, 28 октябрь, 1964 
9. Freedom and Democracy Day : вторник, 17 ноябрь, 1964 
10. Christmas Eve : четверг, 24 декабрь, 1964 
11. Christmas Day : пятница, 25 декабрь, 1964 
And here are the 2 public holidays falling on a weekend:
1. St Cyril and Methodius' Day : воскресенье, 5 июль, 1964 
2. St. Stephen's Day : суббота, 26 декабрь, 1964