Does an AWS Association for automatically start/stop an RDS database adjusts for DST time change?

Question

I created 2 associations to auto start and stop an RDS instance at specific time, every day as instructed here:

https://aws.amazon.com/it/blogs/database/schedule-amazon-rds-stop-and-start-using-aws-systems-manager/

StartRDS at 08:00am UTC/GMT and StopRDS at 20:00 UTC/GMT.

My question is, does this take into account the DST time change that will occur in 2 weeks from now? Should I revisit and adjust manually the time?

Answer 1

By definition, UTC does not observe DST. If you schedule a cron job in terms of UTC then no, it will not take DST rules for your time zone into account.

Keep in mind that the rules for DST are very specific to an individual time zone. Not all time zones use DST, and those that do don't all use the same date and time for their transitions.

That said, it appears the article you pointed to is less about Amazon RDS, and more about using Amazon Systems Manager to schedule maintenance tasks. Indeed, Systems Manager does support scheduling using a specific time zone rather than UTC.

Reference:

• https://docs.aws.amazon.com/systems-manager/latest/userguide/maintenance-windows-schedule-options.html
• https://docs.aws.amazon.com/systems-manager/latest/userguide/reference-cron-and-rate-expressions.html

An example from there is as follows:

aws ssm create-maintenance-window \
   --name "My-LAX-Maintenance-Window" \
   --allow-unassociated-targets \
   --duration 3 \
   --cutoff 1 \
   --start-date 2021-01-01T00:00:00-08:00 \
   --schedule-timezone "America/Los_Angeles" \
   --schedule "cron(0 09 ? * WED *)"

The doc goes on to explain:

... Taken together, the --schedule-timezone and --schedule values mean that the maintenance window runs at 9 AM every Wednesday in the US Pacific Time Zone (represented by "America/Los Angeles" in IANA format). The first execution in the allowed period will be on Wednesday, January 4, 2021, at 9 AM US Pacific Time.

See the list of tz database identifiers to choose the correct one for your time zone.

You can also pick the time zone when creating the schedule via the AWS Console UI.

(Perhaps that option was added sometime after the article was written, as it's not in the screenshot in the article, but does appear presently in the AWS console.)

Choosing the correct time zone will take DST for that time zone into account. In the example shown, the job runs at 9:00 PST (UTC-8) on days when DST is not in effect, or it runs at 9:00 PDT (UTC-7) on days when DST applies.