Fixing Unescaped Character in Date Function

As per the [php.net docs](http://us1.php.net/manual/en/function.date.php#example-681) any function that uses php date syntax should escape *every* literal character not just the first character.

The `f` character doesn't do anything in the php date function so when we have `... \of ...` the `o` escapes correctly and the function still prints the `f` correctly but as soon as someone tries to translate `\of` to anything else like `\de` (Spanish) there are problems:
![screen shot 2013-09-06 at 15 07 15](https://f.cloud.github.com/assets/1065372/1099327/6e718a4c-1734-11e3-98cf-e67055db1153.png)

reference: https://woothemes.zendesk.com/agent/#/tickets/95195