The number of seconds from the current date and time for the new date. Use a negative value to specify a date before the current date.
For doing this we have a method named dateWithTimerIntervalSinceNow(seconds: NSTimeInterval) -> NSDate (Swift) or + (NSDate*)dateWithTimeIntervalSinceNow:(NSTimeInterval)seconds (Objective-C).
Now for example, if you require a date one week from current date and one week to current date, then we can do it as.
let totalSecondsInWeek:NSTimeInterval = 7 * 24 * 60 * 60;
//Using negative value for previous date from today
let nextWeek = NSDate().dateWithTimerIntervalSinceNow(totalSecondsInWeek)
//Using positive value for future date from today
let lastWeek = NSDate().dateWithTimerIntervalSinceNow(-totalSecondsInWeek)let totalSecondsInWeek:TimeInterval = 7 * 24 * 60 * 60;
//Using positive value to add to the current date
let nextWeek = Date(timeIntervalSinceNow: totalSecondsInWeek)
//Using negative value to get date one week from current date
let lastWeek = Date(timeIntervalSinceNow: -totalSecondsInWeek)NSTimeInterval totalSecondsInWeek = 7 * 24 * 60 * 60;
//Using negative value for previous date from today
NSDate *lastWeek = [NSDate dateWithTimeIntervalSinceNow:-totalSecondsInWeek];
//Using positive value for future date from today
NSDate *nextWeek = [NSDate dateWithTimeIntervalSinceNow:totalSecondsInWeek];
NSLog(@"Last Week: %@", lastWeek);
NSLog(@"Right Now: %@", now);
NSLog(@"Next Week: %@", nextWeek);