XSLT counting elements containing a date that is less than another date - xslt

Question

I am trying to generate a .csv from an xml file which includes a count of "OtherEmployees" with a date of birth prior to a date (e.g. 01/01/1970) and I am unsure of the syntax.
Note that the dates are currently in dd/mm/yyyy format.
This is an example of the xml -
<Companies>
<Company>
<CompanyReference>00000060</CompanyReference>
<Contact>
<PersonID>63</PersonID>
<Title>Mrs</Title>
<Forename>EXAMPLE</Forename>
<Middlename/>
<Surname>NAME</Surname>
<DOB>27/05/1928</DOB>
</Contact>
<OtherEmployees>
<OtherEmployee>
<PersonID>28870</PersonID>
<Title>Miss</Title>
<Forename>EXAMPLE</Forename>
<Middlename/>
<Surname>NAME2</Surname>
<DOB>03/05/1953</DOB>
</OtherEmployee>
<OtherEmployee>
<PersonID>28871</PersonID>
<Title>Miss</Title>
<Forename>EXAMPLE</Forename>
<Middlename/>
<Surname>NAME3</Surname>
<DOB>11/07/1961</DOB>
</OtherEmployee>
</OtherEmployees>
</Company>
I was able to get as far as a count of OtherEmployees with a date of birth with the following -
<xsl:value-of select="count(OtherEmployees/OtherEmployee[DOB])"/>
However I now need to compare the DOB with another date - say 01/01/1970 and only return the OtherEmployee in the count if they have a date of birth before 01/01/1970.

Answer 1

With XSLT 2.0 you can make use of the xs:date data type e.g.
<xsl:value-of select="count(OtherEmployees/OtherEmployee[DOB and xs:date(concat(substring(DOB, 7), '-', substring(DOB, 4, 2), '-', substring(DOB, 1, 2))) lt xs:date('1970-01-01')])"/>
With XSLT 1.0 you can easily convert your data format dd/mm/yyyy to a number yyyymmdd and compare on that:
<xsl:value-of select="count(OtherEmployees/OtherEmployee[DOB and number(concat(substring(DOB, 7), substring(DOB, 4, 2), substring(DOB, 1, 2))) < 19700101])"/>