Savings deposits were reclassified from a non-M1 component of M2 into M1 itself. Since M2 ⊃ M1 that change isn't actually reflected in the M2 chart. You can see the M1 chart ~triple overnight when the change was made:

M1

View a measure of the most-liquid assets in the U.S. money supply: cash, checking accounts, traveler's checks, demand deposits, and other che...