The deadline for US income taxes is April 15 in nearly all states. It is only later in 1 or 2 states that have a statutory holiday on the 15th.
If you want to become my tax client send a message to firstname.lastname@example.org by the afternoon of Thursday April 14 giving your name, address, and Social Security Number. I will fill them out and mail them the morning of the 15th.
Of course, if you change your mind and want to have someone else prepare your taxes later that is okay. The extension is 6 months for the tax form 1040 but you are still expected to pay by the 15th of April. The extension is for time of filing, not for paying.
It is not clear at this time whether the extension of time is also for the FBARs needed when your foreign financial accounts sum up to more than $10,000 but it looks like it does.