Can you contribute to a Roth IRA from April to December or is it April to April? (i.e., is it tax year or calendar year?)
The answer is BOTH!
You can contribute to the current year starting January 1. However, up until tax time (April 15) you can elect to contribute to the past year.
April 16, 2007 to December 31, 2007: you can contribute to 2007 tax year only
January 1, 2008 to April 15, 2008: you can contribute to 2008 tax year (current year contribution) or the 2007 tax year (past tax year contribution)
April 16, 2008 to December 21, 2008: you can contribute to 2008 tax year only