import time.{TimeZone, Date, SimpleDateFormat, Hour}

pattern = SimpleDateFormat( 'MMMM d yyyy h:mma zzz' )
date = pattern.parse( 'March 7 2009 7:30pm EST' )
later = Date( date.getTime() + 12 Hour )
println( pattern.format(later) )    // Eastern Daylight Time
pattern.setTimeZone( TimeZone.getTimeZone('America/Los_Angeles') )
println( pattern.format(later) )    // U.S. Pacific Time