What format string do I use for milliseconds in date strings on iPhone?

I'm required to parse strings in a format that includes milliseconds. What format string do I use to get the right date value?

For example, suppose I have a string with the following value: "2011-06-23T13:13:00.000"

What format string do I pass to my NSDateFormatter in the following code?

NSString *dateValue = @"2011-06-23T13:13:00.000";
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
NSString *formatString = @"yyyy-MM-dd'T'HH:mm:ss.???";
[formatter setDateFormat:formatString];
NSDate *date = [formatter dateFromString:dateValue];

What do I use in place of ??? in the code above?

It's SSS, per the Unicode Locale Data Markup Language spec.

"yyyy-MM-dd'T'HH:mm:ss.SSS"

More generally, use any number of upper-case S characters to get that many decimal places in the fractions-of-a-second component. (So ss.S will show the time to the nearest tenth of a second, for example.)

The Date Format Patterns guide suggests that "S" is the format specifier for fractions of seconds.

You need to pass same number of 'S' at the end for example My Date was '2015-11-17T03:36:45.041503Z' the i used 'yyyy-MM-dd'T'HH:mm:ss.SSSSSSz' formatter, I mean see the number of 'S' is 6 as 6 digit coming in date.

use SSS for three decimal places of a second

"yyyy-MM-dd'T'HH:mm:ss.SSS"