I am trying to create a formula that will display an information sentence.

Currently my formula is as follows:
="as of Wk "&OFFSET(Lookup!$E$4,Lookup!$A$10,)&", ending "&DATE(YEAR(TODAY()-1),MONTH(TODAY()-1),DAY(TODAY()-1))

Essentially I want it to say : "as of Wk (insert week num), ending (date)"
For monday of this week it would have said :
"As of Wk 4, ending 1/26/2014"
(notice date is actualy one day behind current date assuming this was Monday)

The offest in the formula is correctly picking up the week. However, the Date part of the formula is formatting as serial number and not date. Suggestions?