是timeIntervalBetween1970AndReferenceDate + timeIntervalSinceReferenceDate = timeIntervalSince1970

Question

我正在看一段代码，偶然发现使用timeIntervalBetween1970AndReferenceDate和timeIntervalSinceReferenceDate。

代码返回的时间戳以毫秒为单位：

return (Date.timeIntervalBetween1970AndReferenceDate + date.timeIntervalSinceReferenceDate) * 1000

这不等于：

return date.timeIntervalSince1970 * 1000

Answer 1

确实，没有区别。 setup_databases具有类型属性

Date

和实例属性

public static let timeIntervalBetween1970AndReferenceDate: TimeInterval
// The number of seconds from 1 January 1970 to the reference date, 1 January 2001

这意味着对于类型为public var timeIntervalSinceReferenceDate: TimeInterval { get } // The interval between the date value and 00:00:00 UTC on 1 January 2001. public var timeIntervalSince1970: TimeInterval { get } // The interval between the date value and 00:00:00 UTC on 1 January 1970. 的任何值date来说，身份都是

Date

按住。实际上，正如我们在Date.swift#L111中看到的那样，Date.timeIntervalBetween1970AndReferenceDate + date.timeIntervalSinceReferenceDate == date.timeIntervalSince1970 的实现方式为

timeIntervalSince1970