Shard `Long` values across N days

ModDate.scala

import cats._
import cats.implicits._
import cats.effect._
import scala.concurrent.duration._

object ModDate {
  def epochDay[F[_]: Clock: Functor]: F[Long] =
    Clock[F]
      .realTime(SECONDS)
      .map(FiniteDuration(_, SECONDS).toDays)
  
  def modToday[F[_]: Clock: FlatMap](nDays: Int)(lst: List[Long]): F[List[Long]] =
    epochDay[IO].flatMap { day =>
      lst.filter { id =>
        id % nDays.toLong === (day % nDays)
      }
    }
}