Perhaps also worth noting:

Script:

$fmt = new IntlDateFormatter('en' ,IntlDateFormatter::FULL, 
IntlDateFormatter::FULL,
    'UTC', IntlDateFormatter::GREGORIAN  ,"WTF 'y-'M");
var_dump($fmt->format(0));

$fmt = new IntlDateFormatter('en' ,IntlDateFormatter::FULL, 
IntlDateFormatter::FULL,
    'UTC', IntlDateFormatter::GREGORIAN  ,"n-'M");
var_dump($fmt->format(0));


Actual:

string(1) "0"
string(1) "-"


Expected:

string(1) "0T1 1970-1"
string(1) "n-1"

Oops, the last expected is of course:

string(1) "n-M"

I discovered this in the ICU documentation:

> Any characters in the pattern that are not in the ranges of ['a'..'z'] and 
['A'..'Z'] will be treated as quoted text. For instance, characters like ':', 
'.', ' ', '#' and '@' will appear in the resulting time text even they are not 
enclosed within single quotes.The single quote is used to 'escape' letters. Two 
single quotes in a row, whether inside or outside a quoted sequence, represent a 
'real' single quote.

Example:

> yyyy.MM.dd G 'at' HH:mm:ss zzz
> 1996.07.10 AD at 15:08:56 PDT

http://userguide.icu-project.org/formatparse/datetime

So the escaping is always between two quote characters, and not an escape 
character before each escaped character (like with date).

Thus, this report is invalid and may be closed.

Invalid, closing.