I did like my original code that used the default Java behaviour of a fall back to GMT for a not recognized timezone, but this has been changed to get a "fall back to server timezone". Anyway, now the code has been changed the info:
timeZone - Timezone. Null or blank means server timezone. If not recognized it will fall back to GMT. should change to: timeZone - Timezone. Null or blank means server timezone. If not recognized it will fall back to server timezone. Martijn Houtman
