First day of the year:
DATE_SUB(CURDATE(),INTERVAL dayofyear(now())-1 DAY)
First day of last month:
DATE_SUB(DATE_SUB(CURDATE(),INTERVAL EXTRACT(DAY FROM CURDATE()) - 1 DAY),INTERVAL 1 MONTH)
Last day of last month:
DATE_SUB(DATE_SUB(CURDATE(),interval EXTRACT(DAY FROM CURDATE()) DAY),INTERVAL 0 MONTH)
First day of the month:
DATE_ADD(CURDATE(), INTERVAL - DAY(CURDATE()) + 1 DAY)
Current date:
CURDATE()
Last day of the month:
DATE_SUB(date_sub(CURDATE(),INTERVAL EXTRACT(DAY FROM CURDATE()) DAY),INTERVAL -1 MONTH)
Last 30 days:
BETWEEN DATE_SUB(CURDATE(), INTERVAL 30 DAY) AND CURDATE()
To be continued…