What is the contribution deadline for an IRA?
Individuals must make regular contributions to Traditional and Roth IRAs by the due date of their federal income tax returns (generally April 15), not including extensions. If the deadline for filing an individual's income tax return falls on a Saturday, Sunday, or legal holiday, he will have until the following business day to make his contribution.
Contributions made between January 1 and April 15 of one year for the previous year are called prior-year contributions.