Get interval to last UTC midnight from an NSDate

Question

I need to compare two times, but one is the current NSDate and the other is an NSTimeInterval. I need to trigger an action when the current time interval since the last UTC midnight gets larger than the given time interval. I'm happy with simply

NSDate *rightNowUTC = [[NSDate alloc] init];

to get current UTC NSDate, but I need to strip it down to "the time interval between whatever *now is and the last time midnight UTC occurred".

Answer 1

NSCalendar provides a method to get the start of the day (midnight) for a given date:

NSDate *rightNowUTC = [[NSDate alloc] init];
NSDate *midnight = [NSCalendar.currentCalendar startOfDayForDate: rightNowUTC];
NSTimeInterval interval = [rightNowUTC timeIntervalSinceDate: midnight];