Structured date display strings are parsed to automatically fill in the fields in the structured date pop-up. The parser is a reimplementation of the XDB fuzzy date parser, which aims to recognize all the formats recognized by the XDB parser, and some additional formats.
Examples of recognized display strings, and the expected results from parsing them, may be found in this test file: testdates.yaml
All recognized display strings are described in this ANTLR 4 grammar: StructuredDate.g4