Date and time calculations often start with a duration in days or seconds.

Convert days to seconds

date_interval_math.swift
import Foundation

let days = 
let duration = DateComponents(day: days)
let secondsPerDay = 24 * 60 * 60
let seconds = duration.day! * secondsPerDay
let message = "seconds=\(seconds)"

print(message)
import Foundation

let days = 
let duration = DateComponents(day: days)
let secondsPerDay = 24 * 60 * 60
let seconds = duration.day! * secondsPerDay
let message = "seconds=\(seconds)"

print(message)
import Foundation

let days = 
let duration = DateComponents(day: days)
let secondsPerDay = 24 * 60 * 60
let seconds = duration.day! * secondsPerDay
let message = "seconds=\(seconds)"

print(message)
duration A fixed duration can be converted into smaller units before a program stores or displays it.