Instance Property
timeIntervalSinceReferenceDate
iOS 8.0+
iPadOS 8.0+
Mac Catalyst 8.0+
macOS 10.10+
tvOS 9.0+
watchOS 2.0+
The interval between the date value and 00:00:00 UTC on 1 January 2001.
var timeIntervalSinceReferenceDate: TimeInterval { get }Discussion
This property’s value is negative if the date object is earlier than the system’s absolute reference date (00:00:00 UTC on 1 January 2001).