'Compute the delta in seconds for the current UTC offset
@param utc_offset: the offset (override defaults)
@return: the offset in seconds'

def delta(self, utc_offset=None):

    if (utc_offset is None):
        utc_offset = self.utc_offset
    if (utc_offset is None):
        utc_offset = current.session.s3.utc_offset
    return S3DateTime.get_offset_value(utc_offset)
