Swift - check if a timestamp is yesterday, today, tomorrow, or X days ago

Question

I'm trying to work out how to decide if a given timestamp occurs today, or +1 / -1 days. Essentially, I'd like to do something like this (Pseudocode)

IF days_from_today(timestamp) == -1 RETURN 'Yesterday'
ELSE IF days_from_today(timestamp) == 0 RETURN 'Today'
ELSE IF days_from_today(timestamp) == 1 RETURN 'Tomorrow'
ELSE IF days_from_today(timestamp) < 1 RETURN days_from_today(timestamp) + ' days ago'
ELSE RETURN 'In ' + days_from_today(timestamp) + ' ago'

Crucially though, it needs to be in Swift and I'm struggling with the NSDate / NSCalendar objects. I started with working out the time difference like this:

let calendar = NSCalendar.currentCalendar()
let date = NSDate(timeIntervalSince1970: Double(timestamp))
let timeDifference = calendar.components([.Second,.Minute,.Day,.Hour],
    fromDate: date, toDate: NSDate(), options: NSCalendarOptions())

However comparing in this way isn't easy, because the .Day is different depending on the time of day and the timestamp. In PHP I'd just use mktime to create a new date, based on the start of the day (i.e. mktime(0,0,0)), but I'm not sure of the easiest way to do that in Swift.

Does anybody have a good idea on how to approach this? Perhaps an extension to NSDate or something similar would be best?

Answer 1

Swift 3/4/5:

Calendar.current.isDateInToday(yourDate)
Calendar.current.isDateInYesterday(yourDate)
Calendar.current.isDateInTomorrow(yourDate)

Additionally:

Calendar.current.isDateInWeekend(yourDate)

Note that for some countries weekend may be different than Saturday-Sunday, it depends on the calendar.

You can also use autoupdatingCurrent instead of current calendar, which will track user updates. You use it the same way:

Calendar.autoupdatingCurrent.isDateInToday(yourDate)

Calendar is a type alias for the NSCalendar.