Assets purchased in prior year need to be depreciated based on in-service date, not date of purchase

I have a Finance user who has several assets that were purchased 5/31/06.  They were not put into service, however, until 1/1/09.  He would like them to start depreciating on 1/1/09 with a 3 year life, but when he ran the depreciation, it calculated based on the purchase date.  As a workaround, he changed the life to 6 years to adjust the monthly expense down to a realistic number, but is wondering if there's a way to change the start of the depreciation to the in-service date.  Thanks!