scheduler.scala

import org.joda.time._
import monix.execution._
import monix.execution.Scheduler.Implicits.global
import java.util.concurrent.TimeUnit
import scala.util.control.NonFatal

def scheduleOncePerDay(time: LocalTime, now: DateTime = DateTime.now())(cb: () => Unit)
  (implicit s: Scheduler): Cancelable = {
    
  val nextTick = {
    val next = now.toDateTime(DateTimeZone.UTC).withTime(time)
    if (next.compareTo(now) <= 0) next.plusDays(1).getMillis else next.getMillis
  }
    
  s.scheduleOnce(nextTick - now.getMillis, TimeUnit.MILLISECONDS, 
    new Runnable {
      def run(): Unit = {
        try cb() catch {
          case NonFatal(ex) => s.reportFailure(ex)
        }

        // Next please!
        scheduleOncePerDay(time)(cb)(s)
      }
    })
}

Thanks!

So my initial approach, namely scheduling a 'tick' every 55 minutes, and then checking if the getHourOfDay is 9, is wasteful? It's wasteful since I'm not, per your above example, precisely identifying when to fire the next tick, but I'm dumbly checking every 55 minutes's tick if it's the 9th hour of the day?