convert epoch timestamp to datetime field when importing using ssis into sql server... how?

all:


I am importing an xml file from a 3rd party vendor and their datetime fields are epoch timestamps.
I need to convert these into a datetime field as im importing into my sql server table.

Ive played around with this in SSIS, but I am new to SSIS and cannot find a resolution.  The best I have done is make the .xsd file data types for those epoch datetime fields a ws:string type and also make my corresponding fields in sql server nvarchar datatypes. 

I can get the data to import that way fine, but then when im trying to write report queries, it makes the sql really a pain.

I tried using a derived column, but cannot figure out how to do that properly.

Can someone direct me to the proper way to handle this conversion please?

If you need more information, i will be happy to supply.

Again -- its a epoch timestamp field in an xml file that needs to be converted to datetime field and imported into my sql server table that will have a datatype of datetime.

Thanks!