We execute your orders seven days a week. If your order's execution time comes, but markets are closed, we'll execute your order with the price of the previous market day's close.
For example, if you have selected €100 of $APPL to be one of your savings plans and the price skyrockets overnight by 5%, you will see €105 worth of Apple Fractional Shares in your savings plan pocket on the morning of the selected day.
In all other cases and instruments, the actual market price is taken for the moment the order is fulfilled.