If you’re wondering when to celebrate the Uposathas, the following calendars help!
I really appreciated this lovely .ical file which allowed me to import all the Full Moons/New Moons/Buddhist holidays etc., into my Calendar app, which came from this page:
https://forestsangha.org/community/calendars/year_planners/2018
There’s also a nice PDF there, which shows the Uposathas used pretty much all throughout Thailand (vs. actual astrological full moons/new moons), at least in the Maha Nikaya sect of Thai Theravada Buddhism.