I have the following event to make a journal entry for:

1/27- Big Apple Bikes in New York City is expanding to another location in New York and needs to stock the new location. GBI received a phone order from Big Apple for $232,315 in bicycles and $108,490 in bicycle accessories and safety gear at special discount prices. The cost of the bicycles in this order is $169,586 and the cost of the accessories is $65,094. Big Apple will have a contract trucking company pick up the order when it is ready. The order is sent to GBIs warehouse for picking and packing which may take a couple days. Payment terms to Big Apple for this order are net 30.

1/31- Big Apples truck arrived at GBIs warehouse and picked up the order from January 27^th.

I believe I know the accounts and balances to debit/credit, I just do not know on what day they should be posted. On 1/27 or 1/31?