getDateField

public Date getDateField(final String fieldName) {
        final Object fieldValue = getField(fieldName);
        if (fieldValue == null) {
            return null;
        }
        if (fieldValue instanceof Long) {
            return new Date((Long) fieldValue);
        }
        if (fieldValue instanceof Date) {
            Date fieldDateValue = (Date) fieldValue;
            return new Date(fieldDateValue.getTime());
        }
        throw new IllegalArgumentException("Field " + fieldName + " in " + dataDefinition.getPluginIdentifier() + '.'
                + dataDefinition.getName() + " does not contain correct Date value");
}