Personally, I prefer to tackle problems like this one by availing myself fully of packages such as Date::Calc and Date::Calc::Object, instead of trying to write the necessary calculations in terms of the SQL language variant that I am presently dealing with.   I will perform the date calculations within my program, then provide those computed values as placeholders within the queries that I am to execute.   (Notice that I do not insert them into the SQL text.)

Furthermore, one extremely important (possible...) consideration that you must bear in mind is:   time zones.   If the server is in Portland, Oregon USA and you are in Richmond, Virginia USA, the time-value that you compute locally is three hours “off.”