You become age 65 on the first moment of the day before the anniversary of your birth corresponding to age 65. Thus, you must have been born on or before December 15, 1934 to be at least age 65 on December 14, 1999 and to qualify for SVB.
source: 68 FR 16418, Apr. 4, 2003, unless otherwise noted.
cite as: 20 CFR 408.214