What unit of time does timeIntervalSinceDate return?

Question

What unit of time does timeIntervalSinceDate return? Is it seconds, milliseconds or something else?

The documentation says that it returns an NSTimeInterval, but what unit of time is that value?

From [NSTimeInterval reference](http://developer.apple.com/library/mac/documentation/Cocoa/Reference/Foundation/Miscellaneous/Foundation_DataTypes/Reference/reference.html#//apple_ref/doc/uid/20000018-SW69): Used to specify a time interval, in seconds. `typedef double NSTimeInterval;`. NSTimeInterval is always specified in seconds — albertamg, Jul 22 '11 at 22:50

score 97 · Accepted Answer · edited Dec 10 '20 at 23:09

97

It returns the number of seconds, as an NSTimeInterval value.

NSTimeInterval is always specified in seconds; it yields sub-millisecond precision over a range of 10,000 years.

edited Dec 10 '20 at 23:09

AmitaiB

answered Jul 22 '11 at 22:47

esqew

6

`NSTimeInterval` isn't really an object. It's just a double value. – BoltClock Jul 22 '11 at 22:47
4

Actually, `NSTimeInterval` is _always_ specified in seconds. – GarlicFries Jul 22 '11 at 22:49
1

How do I get at the milliseconds if it's in seconds? – Moshe Jul 22 '11 at 22:53
6

Since 1 second = 1000ms, `[NSDate timeIntervalSinceDate:foo] * 1000` should be milliseconds. – esqew Jul 22 '11 at 22:58
1

@esqew - Ah, I forgot about that. NSTimeInterval has a decimal point - and numbers following it. – Moshe Aug 01 '11 at 14:26

score 7 · Answer 2 · answered Jul 22 '11 at 22:48

Well the NSDate docs show the function prototype as:

- (NSTimeInterval)timeIntervalSinceDate:(NSDate *)anotherDate

And the Foundation Data Types doc states:

NSTimeInterval is always specified in seconds; it yields sub-millisecond precision over a range of 10,000 years.

2 Answers2