For an event that occurs on the same day of each month, use xsd:recurringDay : recurringDay « XML Schema « XML Tutorial

1. XML Tutorial
2. XML Schema
3. recurringDay

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="payday" type="xs:recurringDay" />


</xs:schema>


File: Data.xml

<?xml version="1.0"?>
<payday>---30</payday>