# Set Cancellation Windows v0 (legacy)

Slot-level cancellation windows can be enabled by returning the
`last_online_cancellable_sec` field in
[CheckAvailability](https://developers.google.com/actions-center/legacy/reference/booking-server/checkavailability-method) responses. For example:

### JSON

```json
    /v3/CheckAvailability Response JSON:
{
slot {[...]},
count_available: 1,
last_online_cancellable_sec: 1552930200
}
 
```