I haven't been able to get AWS support on the line and need an answer asap - do the SQL instances on Amazon Web Services RDS use daylight savings? I know the timezone is UTC but not sure if it uses DST....
UTC does not have daylight savings time.
UTC does not change with a change of seasons, but local time or civil time may change if a time zone jurisdiction observes daylight saving time (summer time). For example, local time on the east coast of the United States is five hours behind UTC during winter, but four hours behind while daylight saving is observed there.
As previously stated, UTC does not observe daylight savings. Hence it's "universal" nature.
However, if your application is telling MySQL to change timezones when it connects with
SET TIMEZONE = 'Europe/London'; for instance, then your RDS's
NOW() and other time related functions WILL observe daylight savings.
If you (or your application) does not set the timezone upon connect (with RDS it's impossible to change the timezone within MySQL's global configuration), then it will behave as such with UTC, and not observe any daylight savings rules.