I'm having trouble getting time as context selector in the new UX. Do I need to create a new time module?
New UX will not allow you to publish context selectors if it is not the dimension of your module. Also It will automatically take it as context selectors if it is placed in Pages section of your module.
If you do not have Time as a dimension in any of the modules and you wish to place Time as context selectors then yes you will have to create dummy module and publish the dummy module on to Pages, New UX will take that as a context selector.