The earliest date at which the network load should begin.
- iOS 11.0+
- macOS 10.13+
- UIKit for Mac 13.0+Beta
- tvOS 11.0+
- watchOS 4.0+
For tasks created from background
URLSession instances, this property indicates that the network load should not begin any earlier than this date. Setting this property does not guarantee that the load will begin at the specified date, but only that it will not begin sooner. If not specified, no start delay is used.
This property has no effect for tasks created from nonbackground sessions.