Import Excel Table to SQL Server - with date column
Internally, Excel stores dates as an integer value. I've run into this before and solved it both in SSIS and straight TSQL 

https://stackoverflow.com/questions/9085928/reading-in-date-column-if-first-row-isnt-a-date-with-ssis-excel-data-source/9086831#9086831

In your case, you might need to make a computed column that actually applies the formula, assuming you don't have to worry about the 1900 date.

-- code approximate as I'm late for a meeting
ALTER TABLE tbTableTest1
ADD opActualDate AS DATEADD(day, opDate - 1,CAST('1899-12-31' AS datetime))