Throughout JoJo's Bizarre Adventure, there are a few cases where the timeline does not match up with previously stated dates or dates end up being changed in future chapters, creating inconsistencies.
One of the largest contradictions in the series is the date that Stardust Crusaders took place. Stardust Crusaders has a journey taking fifty days, beginning either in the end of 1987 and concluding in the start of 1988, or beginning in the end of 1988 and concluding in the start of 1989.
- Josuke is said to be born in 1983 and was four years old when he gets his fever.
- In the anime, Keicho states that his dad starts mutating when DIO was defeated eleven years ago in 1988, when Okuyasu was four years old.
1988 is used in the Part 4 manga and Part 6, with several things in Stone Ocean being based on Part 3 taking place in 1988.
- Jotaro hasn't stopped time in 10 years, meaning since his battle against DIO in 1989 since Part 4 takes place in 1999.
- Jotaro says DIO got his stand in 1988. He and Keicho also say the battle against DIO occurred "10 years ago". Keicho mentions that Okuyasu was five years old at this time in the manga, which is inconsistent since Josuke was four when he got his fever.
- Pucci was born in 1972 and was 16 when meeting DIO, who he says he met in 1988. The two have met more than once, which wouldn't be possible if DIO died in early 1988 as DIO would have to travel back and forth from Florida to Egypt.
- Pucci says that Jotaro burned DIO's diary in 1989 after he defeated DIO.
Jotaro is 28 in Part 4 (1999-28=1971, 1971+17=1988) and 40 in Stone Ocean (2011-40=1971). However, his birth date is said to be 1970 in JoJo6251. Considering his manga biography also states that his zodiac sign is Aquarius in Part 3, his birthday would be in either January or February and Part 4 begins in April, meaning he should actually be 29.
The anime attempts to keep the date consistent with the year Part 3 took place being 1987, but they keep Jotaro's age being 28 in Part 4. His birth year and zodiac were never stated in the anime, so his birthday may just end up being later in the anime timeline.
Diamond is Unbreakable
Chapter 266 states Part 4 begins in March 1999, while JoJo6251 states Jotaro meets Josuke in April 1999.
Narancia was originally born in 1984 with a Leo zodiac sign in Chapter 472. This date and zodiac is kept in the anime, despite his birthday later being changed to May 20, 1983 with a Taurus zodiac sign in Chapter 572.
In Chapter 500, Melone states that Bucciarati is an Aries while checking his compatibility with Baby Face's mother. However, Bucciarati's profile in Chapter 590 reveals that his birthday is September 20, making him a Libra.
Steel Ball Run
Funny Valentine's Age
Steven Steel's Age
In SBR Extra Chapter 1, Steven Steel is said to have been born in 1840, but in the same chapter is stated to be 51, despite Steel Ball Run being set in 1890. However, in SBR Chapter 64, Steven's age is listed as 53.
Stage 8 of the race starts on December 28, 1890 and is said to last 2 days, whereas the final stage afterwards lasts approximately 30 minutes. However, the date is somehow January 19, 1891 by the time the race finishes.
Norisuke Higashikata I's Age
Norisuke I's birthday is stated to be in 1846, yet he is also said to be 68 years old when Part 7 takes place in 1890. If he was born in 1846, he would only be 44 years old, a year older than Funny Valentine during the race.
Tsurugi was originally 2 years old in the Ultra Jump release of JJL Chapter 7, but was corrected to 9 years old in the volume release. By JJL Volume 22, Tsurugi has aged to 10 years old. Later in a flashback in JJL Chapter 107, Jobin mentions Tsurugi is 11, however the flashback occurs at some point after Ozon Baby's Pressure arc, but before The Wonder of You (Your Miraculous Love) arc, contradicting Tsurugi's stated age during the events of The Wonder of You (Your Miraculous Love) arc.
In the Ultra Jump release of JJL Chapter 57, the text on the cover states that Joshu is 19 years old. However, this is not mentioned in JJL Volume 14 and onwards, which lists him as being 18 on the summary pages.
Day of the Harvest
In JJL Chapter 89 p. 4, the day Josuke was framed for the death of an hospital patient is said to be on the 19th. That day, Rai Mamezuku said that the Harvest was in six days, putting the date on the 25th. In the same chapter from page 12 to 15. We also learn that a lecture by Satoru Akefu will happen "tomorrow" on the 21st, and that the Harvest will be in "48 hours". Thus a second date for the harvest set for the 22nd can be extrapolated from this information.
Thus Spoke Kishibe Rohan
Rohan is stated to be 27 years old in Millionaire Village. In the chapter, Kyoka mentions that an event in 1989 occurred 23 years ago, meaning the story takes place in 2012. Rohan would be 33 in 2012 since he was born in 1979. This is fixed in the OVA, as Kyoka doesn't mention how long it's been since 1989.