Well it may not exactly be 20 years if you were born on October 7 1999 and it is January 1st 2019 then it would be 19 years. But assuming that it is the exact date then it would be 20 years. Also we are forgetting about leap days. If you were born on May 4th 1999 and it is May 3rd 2019 you are technically 20 years old. But I am not really sure if that really counts.
