stretchRange.scala

  case class Stretch(
   before: Int,
   after:  Int
  )

  case class MidnightRange(
   start: Int,
   end:   Int
  )

  sealed trait Stretched
  def Stretched[A]( a: A ): A @@ Stretched = Tag[A, Stretched]( a )

  sealed trait MidnightRangeValue
  sealed trait Start extends MidnightRangeValue
  def Start( i: Int ): Int @@ Start = Tag[Int, Start]( i )
  sealed trait End extends MidnightRangeValue
  def End( i: Int ): Int @@ End = Tag[Int, End]( i )

  implicit class StretchExtensions( val stretch: Stretch ) extends AnyVal {
    def taggedStart: Int @@ Start =
      Start( stretch.before )
    def taggedEnd: Int @@ End =
      End( stretch.after )

  }

  implicit class MidnightRangeExtensions( val m: MidnightRange ) extends AnyVal {
    def taggedStart: Int @@ Start =
      Start( m.start )
    def taggedEnd: Int @@ End =
      End( m.end )

  }

  trait Stretchable[A <: MidnightRangeValue] {
    def stretch( v: Int @@ A, delta: Int @@ A ): Int @@ A
    def insideBound( v: Int @@ A ): Boolean
  }

  object Stretchable {
    def apply[A <: MidnightRangeValue: Stretchable]: Stretchable[A] = implicitly[Stretchable[A]]

    implicit object StrechStart extends Stretchable[Start] {

      val lowerStretchBound = DateTimeConstants.MILLIS_PER_HOUR * 8

      def stretch( v: Int @@ Start, delta: Int @@ Start ): Int @@ Start =
        Start( Tag.unwrap( v ) - Tag.unwrap( delta ) )

      def insideBound( v: Int @@ Start ): Boolean =
        Tag.unwrap( v ) >= lowerStretchBound
    }

    implicit object StrechEnd extends Stretchable[End] {

      val upperStretchBound = DateTimeConstants.MILLIS_PER_HOUR * 20

      def stretch( v: Int @@ End, delta: Int @@ End ): Int @@ End =
        End( Tag.unwrap( v ) + Tag.unwrap( delta ) )
      def insideBound( v: Int @@ End ): Boolean =
        Tag.unwrap( v ) <= upperStretchBound

    }
  }

  def stretch[A <: MidnightRangeValue: Stretchable]( v: Int @@ A, delta: Int @@ A ): Int @@ A @@ Stretched = {
    val value = Stretchable[A].stretch( v, delta )
    if ( Stretchable[A].insideBound( value ) ) Stretched( value )
    else Stretched( v )

  }

  def stretchedMidnightRange( start: Int @@ Start @@ Stretched, end: Int @@ End @@ Stretched ): MidnightRange @@ Stretched =
    Stretched( MidnightRange(
      Tag.unwrap( Tag.unwrap( start ) ),
      Tag.unwrap( Tag.unwrap( end ) )
    ) )

  def stretchMidnightRange( m: MidnightRange, s: Stretch ): MidnightRange @@ Stretched = {
    val start = stretch( m.taggedStart, s.taggedStart )
    val end = stretch( m.taggedEnd, s.taggedEnd )
    stretchedMidnightRange( start, end )
  }

maybe I went too far?