TimeZones.scala

import java.util.Calendar._
import java.util.GregorianCalendar
import java.util.GregorianCalendar._
import java.util.TimeZone

// A calendar in Paris' time zone (GMT+1)
val cfr = new GregorianCalendar
cfr.setTimeZone(TimeZone.getTimeZone("Europe/Paris"))

// A calendar at GMT+0
val cutc = new GregorianCalendar
cutc.setTimeZone(TimeZone.getTimeZone("UTC"))

// Computes the time difference between the two time zones for a given date
def diff(year: Int, month: Int, day: Int) = {
  cfr.clear
  cutc.clear
  cfr.set(year, month, day)
  cutc.set(year, month, day)
  cfr.getTimeInMillis - cutc.getTimeInMillis
}

diff(1970, JANUARY, 1) // Yields -3600000 => OK
diff(2000, AUGUST, 1)  // Yields -7200000 => OK (daylight savings)

diff(1910, JANUARY, 1) // Yields -561000, or 9 minutes 21 seconds => HUH?