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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 7 public holidays that do not fall during a weekend and we obtain 255 working days in 1980.

Here is the list of these 7 public holidays:

1. Pesach : вторник, 1 апрель, 1980
2. Shvi'i shel Pesach : понедельник, 7 апрель, 1980
3. Yom Ha-Atzmaut : понедельник, 21 апрель, 1980
4. Shavuot : среда, 21 май, 1980
5. Rosh Hashanah : четверг, 11 сентябрь, 1980
6. Sukkot : четверг, 25 сентябрь, 1980
7. Shemini Atzeret / Simchat Torah : четверг, 2 октябрь, 1980

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

1. Rosh Hashanah : пятница, 12 сентябрь, 1980
2. Yom Kippur : суббота, 20 сентябрь, 1980