1987
Subtract 22-2017 and you get the year they were born. Easy peasy.
1998
In 2012, you would have been born in 1990 if you have had your birthday this year. 1989 if you are 22 and haven't had a birthday yet this year.
22 years before the current year (subtract the current year minus 22). Or the year before that, if your birthday is after the current date.
1998
secagawea was born on December 22 and the year was 1852
1988. They are 22 and will be 23 December 22.
1990
She was born July 22, 1998.
He was born in February 22, 1512.
In 2013, a person would have been born in 1991 to be 22 years old in 2013. In 2014, a 22-year-old was born in 1992, depending on which month their birthday falls.
If the person is turning 22 in 2012 they were born in 1990. If they were already 22 in 2012 and will turn 23, they were born in 1989.