Search Operator "until:" does NOT seem to work?


Hello, I found the search operator “until:” does not work now.

You may see, there is a search operator “until” ,as described in the “Tip” of .

However, I type as the example of the tip “ftw until:2012-12-27” into the search box, but ONLY to see “No Tweets result”.
like this

Is this a bug? or this operator has been abolished already??

Thank you in advance for your help.