How to implement proximity search with dates in SOLR

I have a use case where I wanted to find a word near the date of a specific range in the content of a file. Example: Consider this document with content as "income tax for the period January 2011 to January 2012 was $ 2000", Now I have a query like "tax [20110101 TO 20120201]" ~ 4 for which I want to the above document was a hit. I am using complex phrase to handle complex proximity requests.

So can anyone point me in the right direction on how to implement this in Solr.