You should create the order object as part of the checkout experience, and you must confirm the order before it expires. The expires_at field will give you an ISO8601 date time of when that event will happen.

Field	Description
id	A UUID that uniquely identifies this order object.
serial	An auto incrementing value that identifies this order within the supplier.
reference	A human readable version of the serial that can be used by the customer to identify the order.
currency	The currency of the order.
total	The total amount of the order.
balance	The total amount still due in payments. When this value is 0 then the order can be confirmed. This value will be negative to indicate a balance is still due.
confirmed	Whether this order is confirmed or not.
expired	Whether this order has expires or not.
pending	Whether this order is neither confirmed or expired.
confirmable	Whether this order can be confirmed. As in the balance is 0 and it has at least 1 booking.
expires_at	A ISO8601 value indicating when this order is due to expire.
confirmed_at	A ISO8601 value indicating when this order was confirmed.
created_at	A ISO8601 value indicating when the order was originally created.
updated_at	A ISO8601 value indicating the most recent time this order was last updated.
customer[first_name][first_name]	The first name of the customer this booking is for.
customer[last_name][last_name]	The last name of the customer.
customer[email]	The email address for the customer
customer[telephone]	The telephone number for the customer, with the country code. e.g. `+447123456789`