I asked Miguel at
www.lanzaroteinformation.com a couple of weeks ago and again this morning and he sent me the following reply,
"The ayuntamiento still haven't issued the dates - we only had the one for Arrieta over the weekend. But as soon as they do, we'll post them on the site."
We're normally there end July for two weeks and it's normally on during our stay. We're keen to know the date of the fireworks above the harbour!