What dictates when freshclam updates?

[Danny Horne]

Hi all,

I've been trying to figure out what dictates the interval at which
freshclam updates the virus database.  It currently updates every three
hours, but I rebooted my server at midnight last night, expecting
updates to be done at 03:00, 06:00 etc., but they started at 05:00, then
08:00 etc.

/etc/freshclam.conf is set to update every hour (for testing purposes),
but this is ignored (guessing I need to set a cron job, but if that's
the case why offer a time interval in the configuration file).

Just trying to understand the update process.