time <- strptime("March 7 2009 7:30pm EST", "%B%d%Y%I:%M%p%Z") 
isotime <- ISOdatetime(1900 + time$year, time$mon, time$mday, 
   time$hour, time$min, time$sec, "EST")                           
twelvehourslater <- isotime + 12 * 60 * 60                         
timeincentraleurope <- format(isotime, tz="CET", usetz=TRUE)