Convert an NSDate's description into an NSDate?

Question

I store my NSDates to a file in the international format you get when you call description on a NSDate. However, I don't know how to go back from the string-format to an NSDate object. NSDateFormatter seems to be limited to a couple of formats not including the international one. How should I go back from the string-format?

Accepted Answer

Jeff is right, `NSCoding` is probably the preferred way to serialize `NSDate` objects. Anyways, if your really want/need to save the date as a plain date string this might help you:

Actually, `NSDateFormatter` isn't limited to the predefined formats at all. You can set an arbitrary custom format via the `dateFormat` property. The following code should be able to parse date strings in the "international format", ie. the format `NSDate`'s `-description` uses:

```
NSDateFormatter* dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
dateFormatter.dateFormat = @"yyyy-MM-dd HH:mm:ss ZZZ";
NSDate* date = [dateFormatter dateFromString:@"2001-03-24 10:45:32 +0600"];
```

For a full reference on the format string syntax, have a look at the Unicode standard.

However, be careful with `-description` - the output of these methods is usually targeted to human readers (eg. log messages) and it is not guaranteed that it won't change its output format in a new SDK version! You should rather use the same date formatter to serialize your date object:

```
NSDateFormatter* dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
dateFormatter.dateFormat = @"yyyy-MM-dd HH:mm:ss ZZZ";
NSString* dateString = [dateFormatter stringFromDate:[NSDate date]];
```

Convert an NSDate's description into an NSDate?

Solution

Problem