Currently, as of this post, according to the ubiquitously referenced Contacting our Community Moderators knowledge base article, moderators are available Monday-Thursday 9am to 9pm EST and Friday-Sunday 9am to 5:30pm EST.
However, since at least the beginning of March 2017 and probably earlier, I've noticed that the moderators are no longer online after about 5:30pm EST, even from Monday to Thursday. I see this consistently, as I have the moderators on my friends list and I see who is online every time I go to my profile page.
Has Public Mobile changed the moderator coverage hours? If so, could PM please update the hours officially listed in the KB article linked above? This will let members seeking help know when mods are online, and also help active members provide accurate information in that regard. This would be an easy yet useful fix, as it requires editing only one line in an article that is continually referenced by so many members.