Half-BirthDate Calculator (halfbirthday)

HalfBirthdate.scala

import java.time.LocalDateTime
import java.time.format.DateTimeFormatter


object HalfBirthdate {
  val date_2000_02_29: LocalDateTime = LocalDateTime.parse("2000-02-29T00:00:00")

  case class HalfBirthdate(earlierHalfBirthDate: LocalDateTime, laterHalfBirthDate: LocalDateTime) {
    def show() {
      println("Earlier half-BirthDate: " + format(earlierHalfBirthDate))
      println("Later half-BirthDate:   " + format(laterHalfBirthDate))
    }
    def format(datetime: LocalDateTime) = datetime.format(DateTimeFormatter.ofPattern("dd.MM HH:mm:ss"))
  }

  def halfBirthDate(birthDate: LocalDateTime): HalfBirthdate = {
    if (birthDate.getDayOfMonth == 29 && birthDate.getMonthValue == 2) throw new IllegalArgumentException("Can't calculate halfBirthDate when birthDate is on leap day (29.02)")
    val leapBirthDate = birthDate.withYear(2000)
    val shorterYear = birthDate.withYear(2001)
    val longerYear =
      if (leapBirthDate.isBefore(date_2000_02_29)) leapBirthDate
      else leapBirthDate.minusYears(1)

    HalfBirthdate(shorterYear.plusDays(182).plusHours(12),
                   longerYear.plusDays(183))
  }

  def main(args: Array[String]) {
    val birthDate = LocalDateTime.parse("2000-09-15T00:00:30")
    halfBirthDate(birthDate).show()
  }
}