Yep, the date you make the charge to your card.
- So today you make a reservation and give your Disney Visa card for the $200 deposit. You now have 6 months no interest on that $200 deposit amount -- it will be due in July.
- In May you make a partial payment of $1000 towards your reservation, using your Disney Visa. That $1000 now has 6 months no interest, due in November.
- Your final payment is due in August and you put that $2000 on your Disney Visa card. That $2000 now has 6 months no interest, due next February.
Each payment, as long as it is over $100, qualifies for the 6 month no interest. And each payment has it's very own 6-month cycle. They will be listed on your monthly statement, with remaining balance and due date for each.
Enjoy your vacation!