Can't EXTRACT year of the date with BigQuery | error:No matching signature for function EXTRACT

I’m trying to extract the year of a date in order to calculate the age of user.
The ‘birthday’ is a string format in YYYY-MM-DD.

Here is my code

SELECT username, birthday, CURRENT_DATE(),
    EXTRACT(YEAR FROM CURRENT_DATE()) - EXTRACT(YEAR FROM birthday) as age ,    
    FROM 
        `user`;

My SQL table ‘user’:

But the "EXTRACT(YEAR FROM birthday)" don’t work and I don’t find where is the problem.

The complete error :

No matching signature for function EXTRACT for argument types: DATE_TIME_PART FROM STRING. Supported signatures: EXTRACT(DATE_TIME_PART FROM DATE); EXTRACT(DATE_TIME_PART FROM TIMESTAMP [AT TIME ZONE STRING]); EXTRACT(DATE_TIME_PART FROM DATETIME); EXTRACT(DATE_TIME_PART FROM TIME); EXTRACT(DATE_TIME_PART FROM INTERVAL) at [2:41]

>Solution :

Use below

select username, birthday, current_date(),
extract(year from current_date()) - extract(year from date(birthday)) as age ,    
from `user`;        

Note date(birthday) to fix a "problem"