Line 1a on IRS Form 1040ES says "Enter your expected income and profits subject to self-employment tax". My question is... for what date range? Do I do "expected income for the quarter" or expected income for the year 2014, starting on Jan 1, 2014 and ending on Dec 31, 2014? Or is it something else?
I assume you are talking about the "Self-Employment Tax and Deduction Worksheet". Form 1040-ES itself doesn't have a line 1a.
Everything on this worksheet should be figures for the entire year. At the very end (line 17 on the "Estimated Tax Worksheet") you will divide by 4 to get your estimated tax payment for each quarter.