RMA Credit Memo Transaction date and GL Date Issue

Hi

We are facing an issue for all RMA Credit Memo, we have scheduled the auto invoice  program in the interval of 3 minutes.

But each day auto invoice is not picking all the transactions and invoicing, instead there is atime stamp gap of one or two days 

for certain transactions. 

For example 

RMA entered on 26-sep RMA receipt made on 27-sep but the CM transaction date is 1-OCT 

and GL date is 2-OCT and we identified the CM creation date is 2-OCT. 

So would like to know how for the credit memo transaction date and GL date is been derived.