waybar doesn't show calender module

[exotic oasis]

probably means you messed the format up, just at a glance it seems like you have an extra ',' at the end before the '}'
see if removing that helps

heres a custom module example from the man page

Pacman

"custom/pacman": {
"format": "{} ",
"interval": "once",
"exec": "pacman_packages",
"on-click": "update-system",
"signal": 8
}