What is the difference between last_user_update and modify_date?

I'm trying to figure out when a table has been ammended. Using the 2 different sets of code below, i get 2 different answers. Please see below.

Select * from sys.tables where name = 
'AN_StockChecks_000_Specs_010_StockChecks_010_PlantStockCheckSettings'

modify_date

2015-12-07 15:40:58.557

    SELECT OBJECT_NAME(OBJECT_ID) AS DatabaseName, last_user_update,*
    FROM sys.dm_db_index_usage_stats
    WHERE database_id = DB_ID( 'IESA_DWHS')
    AND OBJECT_ID=OBJECT_ID('AN_StockChecks_000_Specs_010_StockChecks_010_PlantStockCheckSettings')

last_user_update

2015-12-10 09:25:43.290