Kim Do-young Needs One Home Run by 6 September. The Record He's Chasing Was Set by a Man Born on a Different Day.

On the evening of 26 August, in the first inning at Gwangju-KIA Champions Field, Kim Do-young turned on a 155km/h fastball from Lotte's Elvin Rodriguez and hit it out for a three-run home run that put KIA in front. It was his 39th of the season, beating the 38 he hit in 2024, which had been his own personal best.

Scouts from the New York Yankees and the Texas Rangers had come to Gwangju to watch.

One more home run and he becomes the youngest player in the history of Korean professional baseball to reach forty in a season. He has until 6 September.

And then, in the middle of all this, somebody looked up the birthday of the man who holds the record, and the whole thing briefly stopped making sense.

The deadline, and how it is calculated

The record belongs to 이승엽 (Lee Seung-yeop), who reached his 40th home run on 23 July 1999, against Hanwha in Daejeon — in 92 games, 428 plate appearances and 341 at-bats, all of them the fewest anyone has needed. He finished that season on 54 and hit 56 four years later, which is still the KBO single-season record.

He was, by the date in the record book, 22 years, 11 months and 5 days old.

Kim Do-young was born on 2 October 2003. Add 22 years, 11 months and 5 days and you land on 7 September 2026 — the day he would exactly equal Lee's age. To break the record rather than tie it, he has to do it on or before the 6th.

It is worth being clear about what that deadline is and is not. It is not the end of the season. The 2026 KBO regular season runs to 7 October, and KIA will keep playing well past the 6th. The deadline is purely arithmetic: after that date, Kim is simply older than Lee was, and no home run can change it.

The birthday

Here is what came out in the last week.

When Lee Seung-yeop joined the Samsung Lions in 1995, the birthday he registered with the KBO was 18 August 1976. That is the date in the record book, and every age-based record about him has been calculated from it for thirty years.

It is his lunar birthday. His solar-calendar birth date — the one on the ordinary calendar — is 11 October 1976.

Recalculate his record on the solar date and he was not 22 years, 11 months and 5 days when he hit his 40th. He was 22 years, 9 months and 12 days. Nearly two months younger.

Which moves the bar. Kim Do-young passed the age of 22 years, 9 months and 12 days on 14 July 2026. On that date he had 27 home runs.

So for a few days there were two live versions of this story running at once: one in which Kim has a fortnight to make history, and one in which the record quietly became unreachable in the middle of July, while he was 13 home runs away and nobody had noticed.

There was a second, smaller argument alongside it about whether leap days should be counted in an age measured to the day.

What the KBO decided

It has now ruled, and the reasoning is the interesting part.

Age-related records — youngest, oldest, all of them — are compiled from the registration data the clubs themselves have submitted, every year, since the league's founding season. Whether a given player registered a lunar date or a solar one is not something the record book adjudicates. The filed date is the date.

On that basis the deadline stands at 6 September, with the leap-day adjustment excluded.

The KBO has also said it will overhaul the whole standard after this season — how birth dates are registered, how age records are computed, and the related question of how foreign players' ages are handled and written.

So the rule is being fixed, but not yet, and Kim's chase runs under the old one.

There is something quietly remarkable in that ruling, and it is not a criticism of it. A national record book is running on paperwork rather than on biography. Lee Seung-yeop was born on a particular day in October 1976; the record says August, because that is what a form said in 1995, and the KBO's position is that the form is what the record is made of. Given the alternative — retroactively recomputing every age record in the league's history against genuine birth dates that in some cases nobody has — it is hard to see what else they could have decided.

It is also a very Korean problem to have. The lunar calendar is not a historical curiosity here; it still governs when Chuseok and Seollal fall, when many families hold ancestral rites, and — for a particular generation — which date got written down when a child was registered.

Why forty is a lot

For a reader used to Major League Baseball, forty home runs may not sound like a landmark.

Two things make it one in Korea. The season is shorter — 144 games now, and 132 in 1999, against MLB's 162. And the ball has been deliberately deadened. In December 2018 the KBO cut the ball's coefficient of restitution and widened its diameter by a millimetre to match the American and Japanese specification, explicitly to end a hitters' era. The effect was immediate and enormous: league-wide home runs fell from 1,756 in 2018 to 1,014 in 2019 — a 42 per cent collapse in a single winter.

Forty-home-run seasons are correspondingly rare. And if Kim gets there, he picks up a second record on the way: he would be the first Korean-born player ever to hit 40 in a season for the KIA franchise. The only 40 in the club's history belongs to Tracy Sanders, an American import, who hit exactly that number in 1999 — the same season Lee Seung-yeop set the record Kim is chasing.

Kim's season

He is hitting .305 with 39 home runs and 98 RBI in 114 games, on-base .404, slugging .643, for an OPS of 1.047. He leads the league in home runs and is not close to being caught.

He is 22. In 2024 he became the youngest player in KBO history to put up a 30-homer, 30-steal season, and won the MVP, a Golden Glove and a Korean Series ring in the same year.

Asked about the record after the 39th, he said he wants to go past forty and follow "이승엽의 길" — Lee Seung-yeop's road.

Which is a more loaded sentence than it first appears, because Lee Seung-yeop's road went to Japan. He spent years with Chiba Lotte and the Yomiuri Giants before coming home to Samsung. He managed Doosan, resigned in June last year, and is now the hitting coach at Yomiuri. The Yankees and the Rangers sending people to Gwangju in August is not unrelated to any of this.

The rain has not helped. KIA's game on 27 August was called off before a pitch was thrown. They are at home to SSG from the 28th.

What it says

The chase itself is straightforward: a very good 22-year-old needs one more swing in ten days, and he is going to get plenty of chances.

What is genuinely unusual is the week the record spent in limbo — not because of anything either player did, but because a form filled in three decades ago used a calendar that most of the world's record books do not know exists. For a few days the answer to "is this the youngest ever?" depended on whether Korean baseball counts the day a man was born or the day he wrote down.

It has chosen the second, for this season at least, and is going to think about it properly over the winter.

Kim Do-young has until the 6th.

For what a Korean baseball crowd is actually like — and why the league sells out on atmosphere rather than results — see KBO cheering, explained. For the other Korean sporting record set this month, by a 106-year-old in Daegu, see the World Masters Championships.

Images. All three are charts we built ourselves: the two versions of Lee Seung-yeop's age and the two deadlines they produce; Kim's home runs by date across the 2026 season; and the three numbers that matter now. There are no photographs. We could find no freely licensed image of Kim Do-young anywhere — nothing on Wikimedia Commons, nothing from Korea.net or KOCIS — and KBO and club photography is all-rights-reserved. South Korea has no freedom of panorama at all, so the stadium is not a route either. Charts only, and we would rather say that plainly than stretch someone else's licence.

Reported from Korean coverage published between 25 and 28 August 2026 — 스포츠경향, 뉴시스, MBN, SBS, 톱스타뉴스, 뉴스경남 and JTBC — together with the KBO's own player records and Samsung Lions' published club history for the 1999 season. We recalculated both age figures ourselves rather than repeating them: 18 August 1976 to 23 July 1999 is 22 years, 11 months and 5 days, and 11 October 1976 to the same date is 22 years, 9 months and 12 days. Both check out, as do the resulting deadlines of 7 September 2026 and 14 July 2026 against Kim's date of birth. Figures are as of the morning of 28 August and this story has a hard expiry: Kim was still on 39 home runs at the time of writing, and either the record falls by 6 September or it does not. Deliberately not asserted: who is second in this year's home-run race, because the numbers we found were inconsistent and stale; the exact games Kim has missed to injury this season, which we could only source to a crowd-edited wiki; and the reason for the twelve-day gap in his home-run log between 31 July and 12 August, which we can see in the data but could not reliably attribute.