android - Creating file with filename containing date crashes the app

Question

I seem to have a problem with some phones, that the app crashes when using the getDate() in a file name saved to the SD Card.

This is my function:

public static String getDate() {

String date;
  Time now = new Time();
  now.setToNow();

date = now.format("%Y-%m-%d_%H:%M:%S");

return date;

}

Any idea why this could be? If I Toast() the getDate() function on the phone, it doesn't crash, but if used with a File name, it crashes every time.