Define a period

...

How many working days in year 1991?

Here is the detail of the calculation:

Because 1991 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 13 public holidays that do not fall during a weekend and we obtain 248 working days in 1991.

Here is the list of these 13 public holidays:

1. Año Nuevo : Tuesday, 1 January, 1991
2. Jueves Santo : Thursday, 28 March, 1991
3. Viernes Santo : Friday, 29 March, 1991
4. Día del Trabajo : Wednesday, 1 May, 1991
5. Batalla de Arica y Día de la Bandera : Friday, 7 June, 1991
6. Día de la Fuerza Aérea : Tuesday, 23 July, 1991
7. Día de la Independencia : Monday, 29 July, 1991
8. Batalla de Junin : Tuesday, 6 August, 1991
9. Día de Santa Rosa de Lima : Friday, 30 August, 1991
10. Combate de Angamos : Tuesday, 8 October, 1991
11. Día de Todos los Santos : Friday, 1 November, 1991
12. Batalla de Ayacucho : Monday, 9 December, 1991
13. Navidad : Wednesday, 25 December, 1991

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

1. Día de San Pedro y San Pablo : Saturday, 29 June, 1991
2. Día de la Independencia : Sunday, 28 July, 1991
3. Día de la Inmaculada Concepción : Sunday, 8 December, 1991