In all honesty it should have been six months ago. New presidents typically get a one year grace period, because obviously it takes a while for policies to come into effect. Personally, in Obama's case, I said he owned it way back in February of 09 because of his signing of the $800 billion stimulus package. But typically after one year you own it. This is why a President's first State of the Union address is so short.
Here is the thing. If you are going to blame Bush for the economy tanking in his last 13 months of office of an 8 presidency after he himself inherited a falling economy and eventually had economic growth for 52 straight months and eventually a 4.8% unemployment rate and eventually a historically low deficit for the first 7 of those 8 years, (and if you didnt even blame Clinton for the falling economy that he inherited), then you must logically blame Obama for his first 18 months in which he has seen an increase in the unemployemnt rate from 7% to 10%, a post WW2 high of debt in spite of TARP being paid back, not to mention an extra 25% dip in the stock market after it had been relatively calm during Bush's last 3 months.
Oh, and lets not forget that we have seen a 2 to 4 fold increase in non government foiled terrorist attacks. Small extra detail there.