The edit history of this page says the initial edit was "copied from meta.SO (with minor modifications)". I can't find anything that it could have been copied from. It is asserted there that moderator elections are held periodically. "Periodically" means the time from one election to the next is always the same. There is no truth whatsoever in that statement. Where is the page that this was copied from?
Maybe the original source of that word is the moderators tab in the list of users
We believe moderation starts with the community itself, so in addition to privileges earned through reputation, we periodically hold democratic moderator elections.
(emphasis mine). This is not a user-editable string, but comes directly from the SE staff.
I also find the use of the word "periodically" confusing. Its usage may be technically correct here, but the fact that it is prone to misunderstandings should be a sufficient reason to change it, from the point of view of user experience.