Converting 12 digit ticks to Date - ios

Question

I am trying to convert 12 digit c# date time ticks formatted time. (648000000000). With the help of following link I added an extension to my code How to get 18-digit current timestamp in Swift?.
extension Date {
init(ticks: UInt64) {
self.init(timeIntervalSince1970: Double(ticks)/10_000_000 - 62_135_596_800)
}
}
let date = Date(ticks: 648000000000)
When I try to see result date it prints following;
0001-01-03 18:00:00 +0000
However, when I try to convert it hour and minute format output is irrelevant like 19:55
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "HH:mm"
dateFormatter.string(from: date)
My first question is how can I format it to get only 18:00. Second is why it is printing 18:00 when I print only date, but 19:55 when I format it?

Answer 1

Just don't subtract 62_135_596_800
extension Date {
init(ticks: UInt64) {
self.init(timeIntervalSince1970: Double(ticks)/10_000_000)
}
}
1970-01-01 18:00:00 +0000
The other problem: When you create date and print it, the string is formatted in UTC time zone (offset GMT+0). But DateFormatter returns string representation dependent on its time zone, which is the local timezone by default.
You can fix your code just by setting dateFormatter's timeZone to UTC
dateFormatter.timeZone = TimeZone(secondsFromGMT: 0)
18:00

Answer 2

Apparently your timestamp represents a duration as the number of 100-nanosecond ticks, not a date. If you divide the number by 10^7 then you get the number of seconds. These can be printed as a duration with a DateComponentsFormatter.
Example:
let ticks = 648000000000
let seconds = TimeInterval(ticks) / 10_000_000
let fmt = DateComponentsFormatter()
fmt.allowedUnits = [.hour, .minute]
print(fmt.string(from: seconds)!)
18:00
The duration is 64800 = 18 * 60 * 60 seconds, that are exactly 18 hours.