The first step we are going to take is to know the etymological origin of the two words that shape the term at hand. Specifically, we can establish the following in this regard:
-Days derived from Latin, exactly from "dies", which means "day".
-Naturals, meanwhile, also comes from Latin. In his case, it emanates from "naturalis", which can be translated as "relative to nature". It is the result of the sum of three differentiated components: the word "natum", which means "born"; the suffix "-ura", which is used to indicate the result of the action; and the suffix "-al", which is synonymous with "relative to".

It is called day to the 24 hour time period , the time it takes for planet Earth to complete a turn on its own axis. According to its characteristics, it is possible to differentiate between different kinds of days.
The natural days are all the days They make up a year. They may be 365 or 366 , depending on whether it is a leap year or not. Within calendar days you can distinguish between business days or working days and the holidays or holidays .
Business days are those considered valid for the development of a activity (labor, administrative, etc.). On holidays, however, these formal activities are not carried out. If we add the business days and holidays of a year, we find the calendar or calendar days .
The determination of business days depends on each region. Many times it is considered that the business days of a week They are Monday, Tuesday, Wednesday, Thursday and Friday, while Saturday and Sunday are not working. In this sense, we can say that a week is made up of seven calendar days (Monday, Tuesday, Wednesday, Thursday, Friday, Saturday and Sunday), of which five are business (Monday, Tuesday, Wednesday, Thursday and Friday) and two no (saturday and sunday).
He month from January , meanwhile, has 31 calendar days . In 2017, it had 22 business days (Monday to Friday, excluding Saturdays or Sundays). However, depending on the year, you can count on 21 or 23, for example. Natural or calendar days, however, remain unchanged.
The month of February is perhaps the most different of all because it has neither 30 nor 31 days. Unlike the others, depending on whether it is a leap year or not, you can count on 28 or 29 days. A situation is that generates a remarkable particularity in people born on February 29 at the time of celebrating their birthday. And there are years in which not existing that day have to celebrate a day before or a day later.
When a procedure or procedure refers to calendar days, it is established that there is no differentiation of days with respect to whether they are business days or not. In this way, if on the 14th it is established that the term of a process ends in five calendar days that means that it will end on the 19th.