Get the length between two dates in hours

Question

I am reading sleep data into my react-native app using react-native-healthkit, and I need to find a way to get the total amount of sleep time. The data is read in like this:

If anyone has any ideas on the best way to handle this data, please let me know.

"The best way to handle this data" is very broad. What part don't you understand? How to turn the strings into dates? How to measure the elapsed time between two dates? All of those things have been completely explained on Stack Overflow already (many times). — matt, Jan 28 '20 at 17:01

score 1 · Accepted Answer · answered Jan 28 '20 at 15:31

extension Date {

    /// Hours since current date to given date
    /// - Parameter date: the date
    func hours(since date: Date) -> Int {
        let calendar = Calendar.current
        let dateComponents = calendar.dateComponents([.hour], from: self, to: date)
        return dateComponents.month ?? 0
    }
}

date2.hours(since: date1)

Using .timeIntervalSince is a bad practice, because some hours may be shorter than other.

score 0 · Answer 2 · answered Jan 28 '20 at 15:29

If anyone has any ideas on the best way to handle this data please let me know.

It really depends on how you're parsing that JSON data. I won't cover JSON parsing here because there are many, many tutorials and blog posts on that topic. Here's one in case you're not sure where to start.

Your goal is to end up with date objects (Date in Swift, NSDate in Objective-C). For example, if you have the values as strings, you can use DateFormatter to parse the strings into Date objects.

Once you have those date objects you can use the operations that those objects supply to get a TimeInterval, which is a double representing an interval in seconds. Convert that to hours by dividing by 3600:

let interval = endDate.timeIntervalSince(startDate)
let hours = interval / 3600

javier rivarola · Answer 3 · 2020-01-28T16:55:54.393

-1

Try this

   let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSSZ"
    guard let startDate = dateFormatter.date(from: "yourStartDate"),
          let endDate = dateFormatter.date(from: "yourEndDate") else {
             return
        }
    let difference = endDate.timeIntervalSince(startDate)

If you are targeting iOS 13 and above you can use

endDate.hours(since: startDate)

instead of timeInterval

edited Jan 28 '20 at 16:55

answered Jan 28 '20 at 16:48

javier rivarola

500
3
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Do not try to second-guess ISO8601DateFormatter by writing your own. – matt Jan 28 '20 at 17:03

Get the length between two dates in hours

3 Answers3