if tDate.Time.IsZero() {
		return nil
	}
	return e.EncodeElement(tDate.Format(time.RFC3339), startElement)
}

// TransitionDays is a type alias to unmarshal Days in Transition
type TransitionDays int

// UnmarshalXML parses number of days from Transition and validates if
// >= 0
func (tDays *TransitionDays) UnmarshalXML(d *xml.Decoder, startElement xml.StartElement) error {
	var days int
	err := d.DecodeElement(&days, &startElement)

		return errXMLNotWellFormed
	}
	return nil
}

// NoncurrentVersionTransition - an action for lifecycle configuration rule.
type NoncurrentVersionTransition struct {
	NoncurrentDays TransitionDays `xml:"NoncurrentDays"`
	StorageClass   string         `xml:"StorageClass"`
	set            bool
}

// MarshalXML is extended to leave out
// <NoncurrentVersionTransition></NoncurrentVersionTransition> tags