Run /kjs custom_command and it will print out the current lunar event ID in chat. Feel free to modify or use for your own scripts, I don't care about credit. It took me way too long to figure this out so I don't want anyone else to have to.
const $TrackedDataKey = Java.loadClass('dev.corgitaco.dataanchor.data.registry.TrackedDataKey')
const $TrackedDataRegistry = Java.loadClass('dev.corgitaco.dataanchor.data.registry.TrackedDataRegistry')
ServerEvents.customCommand('checkLunarEvent', event => {
let key = $TrackedDataKey.fromID($TrackedDataRegistry.of('dataanchor:level'), 'enhancedcelestials:lunar_forecast')
event.player.tell(event.level.dataAnchor$getTrackedData(key).get().currentLunarEventHolder().unwrapKey().get().location())
})