Swift - Not enough bits to represent the passed value - ios

Question

Below code works fine on iOS devices and watchOS simulator.
static func getEventDateTime(startDateTime: Date?) -> String {
if let startDateTime = startDateTime {
let startTimeInMillis = Int(startDateTime.timeIntervalSince1970 * 1000)
let fiveMinutesInMillis = 300000
let eventStartDateTime = Date(timeIntervalSince1970: TimeInterval((startTimeInMillis-fiveMinutesInMillis)/1000))
return convertDateToString(eventStartDateTime)
}
return ""
}
However when I run it on Apple Watch Series 3, I get the following error: double value cannot be converted to int because the result would be greater than int.max on line let startTimeInMillis = Int(startDateTime.timeIntervalSince1970 * 1000).
So I changed
let startTimeInMillis = Int(startDateTime.timeIntervalSince1970 * 1000) to let startTimeInMillis = Int64(startDateTime.timeIntervalSince1970 * 1000)
and
let eventStartDateTime = Date(timeIntervalSince1970: TimeInterval((startTimeInMillis-fiveMinutesInMillis)/1000)) to let eventStartDateTime = Date(timeIntervalSince1970: TimeInterval((Int(startTimeInMillis)-fiveMinutesInMillis)/1000)).
Now I am getting following error: Not enough bits to represent the passed value on line let eventStartDateTime = Date(timeIntervalSince1970: TimeInterval((Int(startTimeInMillis)-fiveMinutesInMillis)/1000))
How do I change the function to make it work on Apple Watch Series 3 or watchOS 7?
Updated function code:
static func getEventDateTime(startDateTime: Date?) -> String {
if let startDateTime = startDateTime {
let startTimeInMillis = Int64(startDateTime.timeIntervalSince1970 * 1000)
let fiveMinutesInMillis = 300000
let eventStartDateTime = Date(timeIntervalSince1970: TimeInterval((Int(startTimeInMillis)-fiveMinutesInMillis)/1000))
return convertDateToString(eventStartDateTime)
}
return ""
}

Answer 1

Use the Calendar API to add/subtract time units (doesn't support milliseconds, but does support nanoseconds, which can be converted from): https://developer.apple.com/documentation/foundation/calendar.
func getEventDateTimeCal(startDateTime: Date?) -> String {
if let startDateTime = startDateTime,
let date = Calendar.current.date(byAdding: .minute, value: -5, to: startDateTime) {
return convertDateToString(date, startDateTime)
}
return ""
}
But also, if you don't need millisecond precision, subtract seconds from TimeInterval. Note that TimeInterval is typealias TimeInterval = Double and always represents seconds.
func getEventDateTime(startDateTime: Date?) -> String {
if let startDateTime = startDateTime {
let fiveMinutesInSeconds = 5.0 * 60
let eventStartDateTime = Date(timeIntervalSince1970: startDateTime.timeIntervalSince1970 - fiveMinutesInSeconds)
return convertDateToString(startDateTime, eventStartDateTime)
}
return ""
}