How do you compare just the time of a Date in Swift?

Question

I have two Date Objects:

1. 2017-01-13 11:40:17 +0000

2. 2016-03-15 10:22:14 +0000

I need to compare

Answer 1

Let say we got two dates in string format:

// "2017-01-13 11:40:17 +0000"
// "2016-03-15 10:22:14 +0000"

We need to convert this strings to Date format, we create DateFormatter() and set the format ("yyyy-MM-dd' 'HH:mm:ssZ") it gonna convert

//date formatter converts string to date in our case
let firstDateFormatter = DateFormatter()
firstDateFormatter.dateFormat = "yyyy-MM-dd' 'HH:mm:ssZ"

Now we can get our date from string to Date format

   //convert string to dates
    if let date1 = firstDateFormatter.date(from: "2017-01-13 09:40:17 +0000"),
        let date2 = firstDateFormatter.date(from: "2016-03-15 10:22:14 +0000") {
    

What we want is to compare only Hours and Minutes. So change dateformat to "HH:mm"

//we ve got the dates, now switch dateformat for other job
firstDateFormatter.dateFormat = "HH:mm"

Now get the string value from our date, that only contain "HH:mm"

   // convert date to string ( part of string we want to compare )
        let HHmmDate1 = firstDateFormatter.string(from: date1) //"17:40"
        let HHmmDate2 = firstDateFormatter.string(from: date2) //"18:22"

Final step is to get date from our "HH:mm" values, let say we ask DateFormatter to give us a date, based on time only, in our case "17:40" and "18:22". DateFormatter will put some values for dates, so we get Jan 1, 2000 automatically for both dates, but it will get the time we provide.

   //produce "default" dates with desired HH:mm
    //default means same date, but time is different
        let HH1 = firstDateFormatter.date(from: HHmmDate1) //"Jan 1, 2000 at 5:40 PM"
        let HH2 = firstDateFormatter.date(from: HHmmDate2) //"Jan 1, 2000 at 6:22 PM"

Now we could easily compare dates

 //compare
        HH1! > HH2!
}

There are many options to compare dates with Calendar also