Question: Today a very weird bug (or so I believe) started occurring. Here is the piece of code:

```
let dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "yyyy-MM-dd"
let dateObj = dateFormatter.dateFromString(serviceDate)
dateFormatter.dateFormat = "dd/MM/yyyy"
let serviceDateBr = dateFormatter.stringFromDate(dateObj!)

```

Now comes the strange part. When I set serviceDate = "2016-10-15", for example, it works:

```
let serviceDate = "2016-10-15"
...
print("dateSQL: \(serviceDate), dateBR: \(serviceDateBr)")
--------
Answer = dateSQL: 2016-10-15, dateBR: 15/10/2016

```

On the other hand, when I just change serviceDate to "2016-10-16" it crashes. Not on day 17, 18 or any other. Just 16.

```
let serviceDate = "2016-10-16"
...
print("dateSQL: \(serviceDate), dateBR: \(serviceDateBr)")
--------
Answer = fatal error: unexpectedly found nil while unwrapping an Optional value

```

I already know that this fatal error occurs when the first formatting fails, returns nil and then I try to force unwrap it on stringFromDate(). But I can't see why it fails in first place. Can anyone help me?

If it is relevant, I am using Xcode 7.3.1. This bug occurs on device and simulator.

Many thanks.

Answer: 
I suppose you are living in Brasil.

On October 16, 2016 the daylight saving time changes and there is no 0:00.
I have tried on Xcode 7.3 and it seems work fine and the results 

```
dateSQL: 2016-10-15, dateBR: 15/10/2016

```

cloud you provide more info?