For millions of Asians, it's a new year: farewell to the Year of the Rat and welcome to the Year of the Ox.

The Ox appears in various guises on several countries' stamps, which are used in the billions during the observance of the new year for the exchange of year-end gifts to thank friends for past kindnesses and for settling debts.

In the Chinese lunar calendar, used traditionally in most of Asia, years have animal symbols, and each animal, according to Asian soothsayers and fortunetellers, influences the events of that year and the character of those born under it. Although Japan and Korea officially go by the western Gregorian calendar, they also maintain customs and traditions of the past represented by the 12-animal zodiac imported from China centuries ago. In Vietnam the holiday is called Tet, an unforgettable name in America since the Vietnam war.

The date of the Chinese New Year changes annually but always falls between Jan. 21 and Feb. 19, arriving with the second new month after the winter solstice -- the shortest day of the year. It is Asia's most important holiday.

The most novel representation of the Ox comes from Taiwan. The design is an abstract drawing of the animal, round in form to symbolize union and harmony, and continues an ongoing series of abstractions. It is the second designed by Chaung Chu-mei, one of a number of female stamp designers of Taiwan.

An Ox that is one of the 12 human-faced animals inscribed in relief on the stone wall of the grave of a Korean general appears on a 70-won issue from South Korea. Another 70-won pictures jaegi-chagi, a traditional children's game played by kicking a shuttlecock in the air.

Japan has a custom of picturing the animal of the year by means of a traditional local toy. The production of local toys, made of soil, paper, paste and other materials dwindled in the Meiji period of the last half of the 19th century with the widespread introduction of western toys. But the local toys have made a comeback because many nostalgic Japanese have been attracted by the simple but unique local products.

Similar symbolic -- but not representational -- portrayals of the Ox appear on issues from China, Vietnam, Hong Kong, Macao and North Korea.

The Asian zodiac is said to have had its origin when animals hurried to the bedside of the dying Buddha centuries ago. The first to arrive was the Rat. But the Rat did so by a ruse -- hitching a ride on the back of the Ox and jumping off at the entrance to Buddha's domicile. The Ox was second. Then came the Tiger, the Hare, the Dragon, the Snake, the Horse, the Sheep, the Monkey, the Rooster, the Dog and the Boar.

Soothsayers say Ox people are patient, sturdy and faithful, but eccentric and bigoted. Rat people have charm and self control. Tiger people are courageous and strong-willed but defiant and short-tempered, and so on. Most Asians regard the tiger, even though it arrived third, as the king of beasts and would rather be tigers.

The new year stamps put on gifts and debt payments are small potatoes compared with the billions put on cards. Though mailed within a short period, they constitute a substantial portion of the annual volume.

In Japan, for example, greetings start amassing in vast piles in post offices a few weeks before the new year. Senders obligingly bundle all cards together so they may be set apart from ordinary mail. Incidentally, the cards are printed by the government and are also numbered for a lottery that gives out millions of prizes.

On New Year's Day, while the Japanese are celebrating, thousands of mailmen pedal their bicycles along familiar routes, their bags overloaded with the accumulated cards, returning to the station many times for new loads until all the holiday mail is delivered.

To compensate for their confusing street systems, the Japanese have a unique addressing system that begins with the city and works down to the family name. Roughly it would be similar to Washington, Northwest, Chevy Chase, Connecticut Avenue between Military Road and Legation Street, number and name.

The total of holiday mail is estimated at more than 2.5 billion pieces, close to 15 percent of Japan's annual mail volume.

A new international 36-cent aerogram for higher postage rates featuring the Landsat satellite has just been issued at the Goddard Space Flight Center in Greenbelt. Landsat is an acronym for Land Remote Sensing Satellite System.

Collectors of first-day cancellations have an extended 60-day deadline from the day of issue, which was Feb. 14, and optional ways of ordering.

Aerograms acquired by collectors, which must be folded properly and addressed, should be sent to Customer-Provided Stationery, Postmaster, Goddard Space Flight Center, Md. 20771-9991. No remittance is required.