Check if local time is after midnight in another timezone - swift

Question

I want to check if my local time is after midnight in another time zone.
Specifically, if right now where I am at is 11 PM Saturday, or 1 AM Sunday local time, I want to see if it is the start of a new week in Central Time (after 12 AM Sunday).

Answer 1

You can use Calendar's dateComponents(in: TimeZone, from: Date) to check the time and date in another timezone. For your specific application:
// create current date, central time zone, and get the current calendar
let now = Date()
let centralTimeZone = TimeZone(abbreviation: "CST")!
let calendar = Calendar.current
let components = calendar.dateComponents(in: centralTimeZone, from: now)
if components.weekday == 1 {
print("It is Sunday in Central Standard Time.")
} else {
print("It is not Sunday in Central Standard Time.")
}
What you're doing there is asking the current calendar to give you a full set of DateComponents in the specified timezone. Then components.weekday gives the day of the week as an Int, starting with 1 for Sunday in the Gregorian calendar.
If you want to know more generally if it's "tomorrow" somewhere, here's a simple method:
func isItTomorrow(in zone: TimeZone) -> Bool {
var calendarInZone = Calendar(identifier: Calendar.current.identifier)
calendarInZone.timeZone = TimeZone(abbreviation: "CST")!
return calendarInZone.isDateInTomorrow(Date())
}
if isItTomorrow(in: centralTimeZone) {
print("It is tomorrow.")
} else {
print("It is not tomorrow.")
}
isItTomorrow(in: TimeZone) creates a new calendar of the same type as the current calendar (presumably .gregorian, but you never know) and sets its timezone to the desired one. Then it uses the neat built-in Calendar method .isDateInTomorrow() to check if the current time is "tomorrow" in the target timezone.
There are lots of other ways to do it, and depending on your specific need there may be a built-in method that will save you a lot of work, so it's well worth reading through the docs on Calendar and DateComponents to see what's available.