The task of selecting the new era name falls to the government, and it takes place in strict secrecy.
Senior government officials have stressed that if the new "Gengo" is known to the public before the announcement, it will be replaced.
That's because they don't want the new name being registered as a trademark or used for product names before it becomes official.
There are stringent guidelines for the selection process.
The Prime Minister first chooses experts to present candidate era names.
Then, he requests each expert to make two to five proposals.
The experts need to keep in mind that a "Gengo" cannot merely be a combination of kanji characters. They are asked to explain the meaning and source of each one.
Although the guidelines don't specify what the sources should be, many of the past era names were taken from phrases in ancient Chinese literature. This time around, the government reportedly is considering Japanese literature as inspiration as well.
After the experts make their proposals, the Chief Cabinet Secretary screens the list based on these criteria; First... that it has a positive meaning that represents the ideals of the people;
It's comprised of two kanji characters;
It's easy to read and write;
It hasn't been used as an era name or a posthumous name of an Emperor;
And that it's not a commonly used word or phrase.
Another aspect that was reportedly considered when "Heisei" was chosen for the name of Emperor Akihito's reign was its first letter when written in the English alphabet.
That's because the first letter is widely used as an abbreviation for the year. For example, "H31" stands for Heisei 31, which is this year.
So the government at the time wanted a name with a different first letter. Heisei worked because the most recent era names were Meiji, Taisho and Showa.