SOLR date functions limitation

[duncdrum]

after much testing most of the available functions for working with dates seem to not have the desired effects. I believe this is due to the fact that the available date fields are indexed as strings

https://github.com/StaatsbibliothekBerlin/findex-config/blob/be9eec72a4f6086bd05a3e779a8a860024746da4/SolrCloud/solr_config/schema.xml#L230

the current function performs a string based boost which somewhat approximates the desired effect. But without a field with the appropriate type=date there is not much more we can do about this on our end.