Making the datestyle be SQL on postmaster startup

Hi,

I'm wishing to set the datestyle in my databases to be of type SQL.

I can do this by the following command:

set datestyle = sql;

However, I'd like to do this automatically upon database startup.

I notice that "postmaster" has a potential configuration option that might
let me do this (note: -o):

-o BackendOptions
The postgres options specified in BackendOptions are passed to all backend
server processes started by this postmaster. If the option string contains
any spaces, the entire string must be quoted.

... but can't seem to find any examples of how this should be set. Any
ideas?

Thanks,

Justin