MySQL

DATE_ADD(date,INTERVAL days), DATE_SUB(date,INTERVAL days)
CURRENT_TIMESTAMP(),NOW() return your now time
basically you can also write the string+-INTERVAL unit
it will also return your function results.

Note:
if you want to know the time after sleep(n),you should use SYSDATE(),
However you should note that...
Because SYSDATE() can return different values even within the same statement, and is not affected by SET TIMESTAMP, it is nondeterministic and therefore unsafe for replication if statement-based binary logging is used. If that is a problem, you can use row-based logging.
-->Binary logging makes it unsafe.
-->So please log in one by one.
 ##USE DATE_SUB(your date,last month,number of  days in this month-1(bc you want the first day)) to reach your first day /last day in your calendar!!!