Beginning the new year on a promising note, the Sensex at the Bombay Stock Exchange gained 94 points, or 0.5 percent, to close at a 20-month high of 17,559, today. The Nifty at the National Stock Exchange rose 31 points, or 0.6 percent, to 5,232.Both the exchanges started off the first trading day in the new year 55 minutes earlier, at 9 a.m. Stock markets in Japan, South Korea, Hong Kong and Singapore ended on a mixed note.