Japan's parliament has approved a law to rename a public holiday in honour of World War II Emperor Hirohito.
Experts are divided on Emperor Hirohito's legacy
Showa Day, after the name Hirohito himself chose for his reign, is intended to mark Japan's post-war rebirth as well as look to the future.
But critics say the move will upset other nations, especially China and the two Koreas, who will say it glorifies Japan's often brutal militaristic past.
A similar bill was abandoned in the past, due to political pressure.
But this time the main opposition Democratic Party of Japan backed the bill, which was proposed by the ruling coalition.
The opposition said it now accepted the idea that the holiday would encourage public reflection of the turbulent 63 years of Hirohito's reign, rather than glorify the emperor himself.
The lower house of parliament voted in favour of the Showa Day holiday last month, and on Friday the upper house approved the bill by 202-14.
The chosen date, 29 April, is already a national holiday, currently celebrated as Greenery Day. Under the new law, Greenery Day will be moved to 4 May, which is currently called People's Day.
The Chinese accuse Japan of not confronting its wartime past
Opinion remains divided on Hirohito's legacy. Many Japanese see him as being a benign figure out of touch with his militarist cabinet, while others insist he was intimately involved in the planning of the war.
Following his death in 1989, the holiday marking Hirohito's birthday was renamed Greenery Day - an oblique reference to the late emperor's passion for plants, but one which avoided using his name.
The re-named Showa Day is a more direct reference to the emperor's era.
The bill enacting the new name was promoted by members of Prime Minister Koizumi's Liberal Democratic Party, which argues that Japan has already apologised enough for its past.
But correspondents say the move will upset other Asian nations because it refers to the period when Japanese troops brutally occupied neighbouring states.
Tensions are already high over Japan's perceived failure to acknowledge its past abuses.
Violent anti-Japan protests erupted in China last month over the wording of a Japanese history textbook, as well as Tokyo's push for a permanent UN Security Council seat.