Drupal - How to publish nodes 3 times a day?

Using modules VBO, Rules and Rules Scheduler

About your approach using modules Views Bulk Operations (VBO), Rules and Rules scheduler (submodule of Rules), for which you wrote "it doesn't seem possible to schedule the Rule to run 3 times a day.": that appears to me "a" valid approach.

What you actually need to do is a minor variation of what is explained in the tutorial Hourly tasks using rules scheduler: in your case you should use an offset of 8 hours (instead of just 1).

And as explained also in that tutorial: Initially execute the component manually. (from then on every other 8 hours the rule will be executed again).

Using modules Rules and Rules Once per Day

There is a fairly new module related to rules, i.e. the "Rules Once per Day" module. Here is how it works (as per the comment in issue 2495775, from the module owner):

• You specify a trigger hour on the administration settings page for this module.
• The Rule trigger will then run when cron tasks are first run after the start of that hour. The actual run time will depend on your cron task timings.

The way I understand/Read this (haven't experimented with it yet though) is like so:

• The "Event" will only be triggered when a cron job is run.
• And that event will only be triggered 1 time / day, i.e. "next time cron runs after the trigger hour has passed".

So by creating 3 similar rules, you could have 1 of them run around (say) 6 pm, another one around 2 pm and the ast one at 10 pm.

PS: I'm assuming this question is about D7.