SQL2 String to Date

Hello I want to ask if it is possible to convert a String to Date, because its is not possible to change the datatype to date because production data can't be changed easily.

Here is my first try but it does not work as expected:

SELECT * FROM [nt:unstructured] as ref WHERE ISDESCENDANTNODE(ref,[/content/jobs/jcr:content/jobData]) AND ref.Function='Legal'

AND ref.date >= CAST('07-07-2017' AS date)  ORDER BY ref.date ASC

After converting it I want to order the nodes by the date.