When are new portals added?

Question

Is there a regular time when new portals are added to the game, or is it just whenever the devs do it? For example, are there updates every Monday morning, or the first Tuesday of the month, or is it more irregular than that? Alternatively, is there some notification that new portals have been added?

It would be nice to know, so I could just look for new portals then, instead of all the time. I'm in a city with only a handful of portals, and enough players that new portals will be snapped up right away. I'd like to be that guy ;)

Answer 1

Since 2013-02-22 new portals are added on Friday around 2AM UTC every 1-3 weeks.
I think they add new portals once in a few weeks at no specific time.

First time they added new portals was ~2012-12-18, Source
Second time it was ~2012-12-26, source
Third time ~2013-01-25, source1 source2
Fourth time ~2013-01-30, source1 source2
Fifth time ~2013-02-22, Source
Sixth time ~2013-03-01, Source1 Source2
Seventh time ~2013-03-22, Source
Eighth time ~2013-03-29

Maybe if we see more new portal aditions around Tuesday-Wednesday we can make assumtion that new portals appear in a middle of a week.
[edit]:It seems that portals are added mostly in a middle of the week, Tuesday-Friday.

Althought Niantic Labs employee said recently that they have a new system for adding portals and its going to be much faster. So maybe things will not be the same after 2013-02-17 and maybe new portals be on Fridays.

Btw it was only 3 times they were added after 2013-02-22, so my answer is not 100% accurate.