Why do we need cronttab or equivalent?

Hi, I use crontab for the "coming soon" product . I understand the basics of crontab and why I need it for this product. First explained to me by @cewing awhile ago.

My question is why do we need it? In Plone, you can set the publishing begin/end dates and the content responds. How does the piece of content know that the start/end date of the content has been reached. This is what I use crontab for with the other product (coming soon) What 'action' runs in place of crontab?

So whatever in Plone runs to tell the page to show/hide, how is that different from crontab and why can't we tap into it for other tasks.

Thanks hope you can set me straight :smile:

The piece of content doesn't know this; the view that renders the piece of content compares the effective and expiry dates to the current date time and decides (at rendering time) what to do (whether to display the content or not).

There are Plone and Zope packages that let you set up tasks that run at definable intervals, but you need a cron job to have those packages wake up periodically and check if they need to run those tasks.

Thanks Kim, now I get it.

is not the view, but the catalog tool: it only return brains that are "visible" at any given moment, unless you bypass that with some special attributes: