Jiroemon Kimura, who was born in 1897, was expected to celebrate his astonishing milestone with friends and family, and receive a visit from the mayor of his home city of Kyotango in the west of the country.
Kimura is one of 95 people who will be 100 years old or more in the city's 60,000-strong population.
The centenarian does not smoke and has made it a practice to eat only until he is 80 percent full, a local official told AFP.
He drinks only a''modest'' amount of alcohol, a local report said.
Kimura's motto in life is ''to eat light and live long'', said the official.
Kyotango now wants to find the secret of his longevity and has launched a research project.
''We would like to reserach the eating habits of not only Mr Kimura but also about 50 other old people over 100 years old in the city, '' the official told AFP.
''We are interested in what they eat and how much. We are especially keen to research on how much salt they consume.''
The city of Kyotango, near Kyoto, is sandwiched between the Sea of Japan (East Sea) and a mountain range. It is naturally blessed with good seafood and farm products, the official said.
''We are also interested in knowing what kinds of local food they like to eat and if this helps them live so long,'' he said.
The city plans to compile a recipe book based on the study and unveil it at a symposium about longevity in November, he said.
''We want city residents to know of the secrets of what enables a long life-span but also to attract tourists to this long-living city,'' he said.
AFP