Here are the the latest interest rates for treasury bills on the secondary market with the yield to maturity.
There is zero risk for these bills, unlike CDs. So not sure why one would go with CDs where treasury bills are guaranteed principle and interest, unless there was a significant difference in rates. . just eliminate the individual bank risk. ..
The sweet spot is currently at 26 weeks, however, you can sacrifice a bit of interest and go out up to 52 weeks without losing much.
Resource Center | U.S. Department of the Treasury
Daily Treasury Bill Rates: These rates are the daily secondary market quotations on the most recently auctioned Treasury Bills for each maturity tranche (4-week, 8-week, 13-week, 17-week, 26-week, and 52-week) for which Treasury currently issues new bills. Market quotations are obtained at approximately 3:30 PM each business day by the Federal Reserve Bank of New York. The Bank Discount rate is the rate at which a bill is quoted in the secondary market and is based on the par value, amount of the discount and a 360-day year. The Coupon Equivalent, also called the Bond Equivalent, or the Investment Yield, is the bill's yield based on the purchase price, discount, and a 365- or 366-day year. The Coupon Equivalent can be used to compare the yield on a discount bill to the yield on a nominal coupon security that pays semiannual interest with the same maturity date.