published April, 2011
If you owe estimates for 2011, they’re due. The IRS and states want you to “pay as you go” and this is the first date of the first payment for 2011.
You may also be aware tax returns are due on this day as well. What you may not be aware of is Friday is Emancipation Day in Washington DC, so it is a holiday, so returns are not due until the next business day, not Saturday, not Sunday, but Monday, April 18th. However, it is not a holiday in California, so CA returns are still due on Friday (but CA has suggested they’ll forgive a few days).