Summary: Date Biasing is correctly enabled but when searching expected relevant documents are not returned, it seems the biasing has no effect.
Cause: There is also a known bug pertaining to this (6081241), where the biasing value is unavailable. Infact biasing appears to have a change, but it is impossible due to this bug to determine the exact effect. For date biasing to work, the GSA must also be aware of the document dates, if no dates or incorrect dates are present, then the GSA will not bias results as expected.
Troubleshooting Steps: To determine if the correct date as been extracted we need to observe the FS parameter date value in the xml output. In order to be able to see these values you must remove the "proxystylesheet" parameter from the search URL, this is also described here in the xml reference.
By default this value is taken at crawl time from the last modified date, please ensure that the value is correct, if you need to define specific document date rules, please follow the official documentation for defining document date rules
Regarding relevancy, Sort mode S (eg. sort=date:D:S:d1)works by default by taking the first 1000 documents and then sorting them, if your expected document is not considered relevant or falls outside the default 1000 results, it will not be returned. To rectify this when specifying document date query parameter pertaining to relevancy, please ensure to use the R mode as specified in the xml reference
As stated in the same document the quality filter may also reorder results, to remove this add filter=0 to your search URL
Known Issues: (ref. 6081241), the ScoreBias value for DateBias always returns VALUE="-1".
Versions affected: All.
Versions fixed: Unfixed.