How often a feed regenerates

The cycles a feed's Regenerate select offers. They are OpenCart's own four, because the thing that wakes Product Feed up is the store's own cron.

Cycle	On the form
nothing	By hand only
hour	Hourly
day	Daily
week	Weekly
month	Monthly

A feed is due when a cycle has passed since a run last started on it, so a feed that takes longer than its own cycle is never started on top of itself. A feed that has never run is due the moment you switch its schedule on.

The list calls a feed overdue once its own cycle and a further day have passed since it last generated successfully. The threshold moves with the cycle you chose, so an hourly feed on a store whose cron runs once a day is not called out for being on time, and a monthly feed is not two months stale before anybody is told. It is not a setting, and why is on the settings page.