Most target-date funds are established in 5-year intervals (e.g. maturing in 2030, 2035, 2040, 2045, and so on). There is no set rule if you plan to retire in say, 2033. You can round up to the 2035 fund, or if you have a lower risk tolerance, use the nearer-term 2030 one. You can also choose to put something like 60% of your allocation in 2035 fund and 40% in the 2030 fund.