## Gregorian calendar

The Gregorian calendar or the Western calendar, is one of the two calendars that are used globally in order to determine different dates, such as religious events, national events, and official events. The Gregorian year is based on the year of the birth of Jesus Christ, peace be upon him, where the years prior to the birth are referred to as the years before birth, and the year is formed The Gregorian calendar consists of twelve months: January, February, March, April, May, June, July, August, September, October, November, and December. As for the number of its days, it is 365 days in a simple year, and 366 days in a leap year. (It occurs every four years, with a day added to February).[1]

## Date of Birth

It is the date of birth of an individual, male and female, where the day, month, and year are recorded in official documents, and through this date the individual can calculate how long his age has passed through several arithmetic methods, and this date may be recorded in the Hijri calendar or the Gregorian calendar, depending on the calendar What is followed in his country, and when comparing age with the two calendars, there is a year difference, because there is a difference between the number of days of the Hijri and Gregorian calendar, where the days of the Hijri year are less than the Gregorian year by a difference of ten days.[2]

## How to calculate age according to the Gregorian calendar

Age is calculated using one of the following methods:[3]

- By downloading applications for calculating the age according to the Gregorian calendar on smart devices from Google Play or the Apps Store, where the user selects the date of birth by day, month, and year, and within a few seconds the result will appear to him.
- By using the websites for calculating age, by using the Google search indicator, and typing “calculating age according to the Gregorian calendar”, many options and sites for the calculation will appear. Enter the date of birth with the day, month and year, and the site will automatically calculate the age, in years, days, months, weeks and hours and seconds.
- For simple arithmetic methods, by subtracting the year of birth from the current year, for example, if we assume that the year of birth is 2011 AD, then the age in Gregorian years = (2016 – 2011) = five years.
- In the event that the year of birth is recorded in the Hijri calendar, it must be converted to the Gregorian calendar by using this equation, (Hijri year = (Gregorian year – 622 / 0.97)), and converting the months into parts of the year, where each month represents its number of days, on For example, converting (9/Ramadan/1410) Hijri to Gregorian, the sum of the days of the complete months until the month of Sha’ban is 236 days, and 9 days of Ramadan, the total number of days becomes (245), then we divide the result of the days by the number of days of the Hijri year Total (245 / 355) = 0.6901408, then we add the result to the required Hijri year 1410, (0.6901408 + 1410 = 1410.6901408), and based on the arithmetic equation (Hijri year = (Gregorian year – 622) / 0.97), we substitute the number 1410.6901408 in the place of the year Hijri, we get 1990.269763, where the integer 1990 represents the Gregorian year, and the fraction is multiplied by the number of days of the Gregorian year 365 as follows (0.269763 x 365 = 98), we subtract the number of days of months from 98 (January 31 days + February 28 days + The month of March has 31 days) (98 – 90 = 8), so the Gregorian date becomes 4/8/1990 AD, then we do the subtraction from The current year for calculating the age (2016 – 1990 = 26 years).[4]

## the reviewer

- ↑ “The Gregorian Calendar”, www.timeanddate.com, Retrieved 21-7-2018. Edited.
- ↑ “birth date”, www.dictionary.com, Retrieved 23-6-2018. Edited.
- ↑ “Age Calculator”, www.calculator.net, Retrieved 21-7-2018. Edited.
- ↑ “Birth, Death, and Age Calculators”, www.txbobsc.com, Retrieved 21-7-2018. Edited.

How do I calculate age in AD?