Index-refresh in SQL Server
You can only know when the Statistics were last updated using STATS_DATE.

You can use either of these queries:

SELECT name, STATS_DATE(object_id, index_id), * 
FROM   sys.indexes 
WHERE  name LIKE 'index name'


or 

SELECT name, STATS_DATE(object_id, index_id), * 
FROM   sys.indexes 
WHERE  OBJECT_ID('schema.table') = object_id


When you rebuild an index, it updates its statistics:


  If statistics correspond to an index, the stats_id value in the sys.stats catalog view is the same as the index_id value in the sys.indexes catalog view, and the following query returns the same results as the preceding query. If statistics do not correspond to an index, they are in the sys.stats results but not in the sys.indexes results.