response code 503 and retry-after without PHP

How to respond with 503 and set Retry-After without PHP

[BlueBlizz]

I've made my server respons with an error 503 when the site is currently for maintenance via Apache.
But how to set the retry-after time?
I do not have PHP running, so there has to be another solution.
Via Apache or a html code in the page itself?

Eric

[jdMorgan]

Use mod_headers to set the Retry-After HTTP response header when the custom 503 error file is served.

See the "Header set" directive in Apache mod_headers and the <Files> or <FilesMatch> directives in Apache core.

Jim