US news articles missing out "on" when referring to a day
This is a common elision in US English, yes, though very rarely in British English. It also seems to be done a lot by French speakers who have learnt English, because this elision is always done in French (or rather, it's always been the case in French that one refers to a day simply by saying the day, rather than on the day); I see this done a lot on the France 24 news channel, even by those newsreaders with a British accent.
It is also commonly done with months, eg.
The festival is happening June, and is going to be very popular.