Notes

1) CURDATE() or CURRENT_DATE() -> yyyy-mm-dd
2) CURTIME() or CURRENT_TIME() -> HH:MM:SS
3) Now() or CURRENT_TIMESTAMP() -> yyyy-mm-dd HH:MM:SS
4) DATE -> returns date part (yyyy-mm-dd) from given date;
e.g. SELECT DATE(now());
SELECT DATE('1998-01-02 23:34:34');

5)EXTRACT -> extracts specified unit from given datetime
e.g. SELECT EXTRACT(YEAR_MONTH FROM '1999-07-02')
SELECT EXTRACT(MINUTE_SECOND FROM now())

6) DATE_ADD / ADDDATE: when invoked it adds the interval time to given datetime.
e.g. SELECT DATE_ADD('1998-01-02', INTERVAL 29 DAY);
SELECT ADDDATE('1998-04-02', -31);
SELECT DATE_ADD('1997-12-31 23:59:59', INTERVAL '1:1' MINUTE_SECOND);
=1998-01-01 00:01:00

7) DATE_SUB / SUBDATE: similar to DATE_ADD, difference is it subtracts the interval time from given datetime.
e.g. SELECT date_sub('1997-12-31 23:59:59', INTERVAL '1:1' MINUTE_SECOND);
=1997-12-31 23:58:58
SELECT date_sub('1998-04-02', interval 1 day ); returns = 1998-04-01

8) DATEDIFF -> returns the difference between two given dates
e.g. SELECT DATEDIFF( now(), "2021-07-11");
SELECT DATEDIFF('1997-12-31 23:59:59', '1997-12-30')
9) DATE_FORMAT -> Formats the date value according to the specified format
e.g. SELECT DATE_FORMAT('1997-10-04 22:23:00', '%W %M %Y');

10) CONVERT_TZ
11) STR_TO_DATE