gml:EnvelopeWithTimePeriod 

gml:EnvelopeWithTimePeriod is provided for envelopes that include a temporal extent. It adds two time position properties, gml:beginPosition and gml:endPosition, which describe the extent of a time-envelope.  
Since gml:EnvelopeWithTimePeriod is assigned to the substitution group headed by gml:Envelope, it may be used whenever gml:Envelope is valid.

Element Information

Model

((gml:lowerCorner , gml:upperCorner) | gml:pos{2,2} | gml:coordinates) , gml:beginPosition , gml:endPosition
Children: gml:beginPosition, gml:coordinates, gml:endPosition, gml:lowerCorner, gml:pos, gml:upperCorner

Attributes

QName Type Fixed Default Use Inheritable Annotation
axisLabels gml:NCNameList optional
frame anyURI #ISO-8601 optional
srsDimension positiveInteger optional
srsName anyURI optional
uomLabels gml:NCNameList optional

Source 

<element name="EnvelopeWithTimePeriod" type="gml:EnvelopeWithTimePeriodType" substitutionGroup="gml:Envelope">
  <annotation>
    <documentation>gml:EnvelopeWithTimePeriod is provided for envelopes that include a temporal extent. It adds two time position properties, gml:beginPosition and gml:endPosition, which describe the extent of a time-envelope. Since gml:EnvelopeWithTimePeriod is assigned to the substitution group headed by gml:Envelope, it may be used whenever gml:Envelope is valid.</documentation>
  </annotation>
</element>

Sample