How to decay documents 1 year and 1+ year olders

accroding to the documentation

   "gauss": {
        "date": {
              "origin": "2013-09-17", 
              "scale": "10d",
              "offset": "5d", 
              "decay" : 0.5 

this query will do it as documents with a field value between 2013-09-12 and 2013-09-22 would get a weight of 1.0 and documents which are 15 days from that date a weight of 0.5.

I try to achieve similar but i cant figure out how to weight documents 1 year older than today gets 1.0 and older than 1 year gets 0.5?