import Foundation

// We'll start by getting the current time.
let now = Date()
print(now)

// You can build a Date struct by providing the
// year, month, day, etc. Times are always associated
// with a TimeZone.
let then = DateComponents(calendar: Calendar.current,
                          timeZone: TimeZone(abbreviation: "UTC"),
                          year: 2009,
                          month: 11,
                          day: 17,
                          hour: 20,
                          minute: 34,
                          second: 58,
                          nanosecond: 651387237).date!
print(then)

// You can extract the various components of the date
// value as expected.
let calendar = Calendar.current
print(calendar.component(.year, from: then))
print(calendar.component(.month, from: then))
print(calendar.component(.day, from: then))
print(calendar.component(.hour, from: then))
print(calendar.component(.minute, from: then))
print(calendar.component(.second, from: then))
print(calendar.component(.nanosecond, from: then))
print(then.timeZone)

// The Monday-Sunday Weekday is also available.
print(calendar.component(.weekday, from: then))

// These methods compare two times, testing if the
// first occurs before, after, or at the same time
// as the second, respectively.
print(then < now)
print(then > now)
print(then == now)

// The timeIntervalSince method returns a TimeInterval representing
// the interval between two times.
let diff = now.timeIntervalSince(then)
print(diff)

// We can compute the length of the duration in
// various units.
print(diff / 3600) // Hours
print(diff / 60) // Minutes
print(diff) // Seconds
print(diff * 1_000_000_000) // Nanoseconds

// You can use addingTimeInterval to advance a time by a given
// duration, or with a negative value to move backwards by a
// duration.
print(then.addingTimeInterval(diff))
print(then.addingTimeInterval(-diff))