Milliseconds until midnight (local time) in Swift? [closed] - ios

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I'm am writing an iOS app and I need to know the (whole) number of milliseconds until midnight (that is, 12:00:00.000 the next day) in the user's local time using Swift.
The application is in an expression like this:
let milliseconds_until_midnight : Int;
DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(milliseconds_until_midnight)) {
//do_something
}
How can we do this? Addendum: the type must be Int, as UInt64 is not accepted in this particular situation.

Answer 1

You can use Calendar method nextDate(after:) to get the start of the next day, use Date method timeIntervalSince(date:) to find out the number of seconds until the next day and return it multiplied it by 1000:
extension Date {
var startOfNextDay: Date {
return Calendar.current.nextDate(after: self, matching: DateComponents(hour: 0, minute: 0), matchingPolicy: .nextTimePreservingSmallerComponents)!
}
var millisecondsUntilTheNextDay: TimeInterval {
return startOfNextDay.timeIntervalSince(self) * 1000
}
}
Playground testing:
let milliseconds = UInt64(Date().millisecondsUntilTheNextDay) // 7731021

Answer 2

Here is the code to count down number of seconds before midnight:
extension Date{
// code to get phone's time zone
var localTimeZoneName: String { return TimeZone.current.identifier }
var numberOfMilliSecondsUntilMidnight: TimeInterval?{
let todayDate = self
let tomorrowDate = todayDate.tomorrowAtMidnight
return tomorrowDate.timeIntervalSince(self) * 1000
}
// local time. beginning tomorrow at 12 AM
var tomorrowAtMidnight: Date{
var cal = Calendar.current
cal.timeZone = TimeZone.current
let today = cal.startOfDay(for: self)
return Calendar.current.date(byAdding: .day, value: 1, to: today)!
}
}
To call for anyone who is new to swift:
print(Date().numberOfMilliSecondsUntilMidnight)
I am pretty sure it works because I had to write a custom date class for a due date system.