Date conversion Problem

Dear Experts,

I have a problem in Date conversion in flat file Loading,

In Flat file it has the below format,

03-Mar-04.

But i want to store it in SAP Format (ie), yyyymmdd. I do know how to achieve this. In flat file if we click on Particular date value (03-Mar-04) in the formulae bar it shows that 3/3/2004.

up to PSA it stores (03-Mar-04) format, ie char -9,

I wrote the field routine by using SPILIT and Concatenate statement

My Question is how the SAP system will identify 04 as 2004, bcoz it may be 1904 or 2004?

Please help as this is very urgent.