How to calculate time in hours between two dates in iOS

Question

How can I calculate the time elapsed in hours between two times (possibly occurring on different days) in iOS?

Answer 1

NSCalendar *c = [NSCalendar currentCalendar];
NSDate *d1 = [NSDate date];
NSDate *d2 = [NSDate dateWithTimeIntervalSince1970:1340323201];//2012-06-22
NSDateComponents *components = [c components:NSHourCalendarUnit fromDate:d2 toDate:d1 options:0];
NSInteger diff = components.minute;

NSDayCalendarUnit|NSHourCalendarUnit|NSMinuteCalendarUnit

Change needed components to day, hour or minute, which difference you want. If NSDayCalendarUnit is selected then it'll return the number of days between two dates similarly for NSHourCalendarUnit and NSMinuteCalendarUnit

Swift 4 version

let cal = Calendar.current
let d1 = Date()
let d2 = Date.init(timeIntervalSince1970: 1524787200) // April 27, 2018 12:00:00 AM
let components = cal.dateComponents([.hour], from: d2, to: d1)
let diff = components.hour!