if confirm('use Europe/Paris as timezone?'):

    timezone = 'Europe/Paris'

else:

    import pytz

    while True:

        timezone = raw_input('enter your timezone')

        if timezone in pytz.common_timezones:

            break

dbdriver = repo.system_source.dbdriver

if dbdriver == 'postgres':

    sql("SET TIME ZONE '%s'" % timezone)

for entity in schema.entities():

    if entity.final:

        continue

    change_attribute_type(entity.type, 'creation_date', 'TZDatetime', ask_confirm=False)

    change_attribute_type(entity.type, 'modification_date', 'TZDatetime', ask_confirm=False)

if dbdriver == 'postgres':

    sql("SET TIME ZONE UTC")