A gestation period of about three and a half months. : timeDuration « XML Schema « XML Tutorial

1. XML Tutorial
2. XML Schema
3. timeDuration

File: Schema.xsd

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
  targetNamespace="http://www.java2s.com" xmlns="http://www.java2s.com"
  elementFormDefault="qualified">

  <xs:element name="gestation" type="xs:timeDuration" />
</xs:schema>


File: Data.xml

<?xml version="1.0"?>
<gestation xmlns="http://www.java2s.com">P3M15D</gestation>

Notice that you don't have to specify all of the units. 
Only the initial P is always required. 
If the period contains time data, you must also add the T.