It’s an accessibility regulation. If a government website has to be equally accessible to people who are deaf / hard of hearing, blind, etc. then the website can only be live when services for those people are up. There are some sites that rely on humans to provide backup services like filling out forms, and they only work business hours.

Aeroplan had this until recently too, the website shut down at 9PM PST and re-opened at 6AM PST. Last employee out turn off the servers? What is it about Canadian IT haha.

Looks like this service has business hours as well. Very strange.