lunar calendar.
The Chinese New Year lantern festival is held each year on the 15th day after the new year on the lunar calendar. The Lantern Festival is a lucky day for families to gather together, light lanterns, attend lantern parades and flying lantern releases, set off fireworks and eat round glutinous rice dumplings. It originated as a Buddhist tradition for monks to light lanterns to show respect to Buddha on this date. Emperors ordered the lighting of lanterns in palaces and temples on that night and civilians were all requested to hang up lanterns at home. Now the lantern festival is celebrated all through China and in many cities around the world. (I still use lanterns with candles. It's only dangerous if it is very windy. Best to keep a bucket of water on hand.)