Chronology (safe for episode 1-4).

1988 : Eun-Ho age 1.
Birth year of Joo Eun-Ho. Age 1.

late 90's :
Peoples that important to Eun-Ho and (real) Hae-Ri died in an accident. A funeral ceremony was held, both sisters wore white clothes.

11th Oct 1999 : Eun-Ho age 11.
(real) Joo Hae-Ri wrote about her grandma.
(Earliest shown date Hae-Ri wrote her diary. So probably Eun-Ho and Hae-Ri age gap is lesser than 6 years). 

2006 : Eun-Ho age 18
(real) Joo Hae-Ri still wrote things in her diary. She adore her older sister very much.

late 2011-2012 : Eun-Ho age 23-24.
Eun-Ho and Hyeon-Oh started dating.

2012 : Eun-Ho age 24.
(real) Joo Hae-Ri still wrote things in her diary. She notice her older sister dream is to be an announcer.

4th March 2012 :
(real) Joo Hae-Ri wrote her dream to work in the same place as Eun-Hoo.

11th March 2012 :
(real) Joo Hae-Ri wrote in her diary that Eun-Ho bought her a gift.

2014 : Eun-Ho age 26.
(real) Joo Hae-Ri missing when she is an university student. Presumed 20th February 2014 as the official police report on her as missing person.

2015 : Eun-Ho age 27.
Opening scene of whole series. Joo Eun-Ho dating with Hyeon-Oh. They live in Eun-Ho's home.

20th February 2019  :
Police Official Statement to End Searching of (real) Joo Hae-Ri.

2019 : Eun-Ho age 31.
Another important figure in Eun-Ho's life passed away.

late 2019-2020 : 
Around this time Eun-Ho and Hyeon-Oh broke up. Eun-Ho age 31-32.

2021 : Eun-Ho age 33.
 Around this year, Eun-Ho applied to parking lot job and work as Hae-Ri.

24th January 2024 : 
Joo Eun-Ho first time have a consultation with psychiatrist.

3rd April 2024 :
(alter) Hae-Ri heard for the first time, that she and Eun-Ho shared same physical body. Also at this time the psychiatrist mentioned that Eun-Ho have started seing the psychiatrist for the past 2 months.

2024 : Eun-Ho age 36.
Recent events in the series took place.

Additional Notes :
(alter) Hae-Ri introduced herself to Min-Yeong, she mention 25 yo (first day at parking lot job).
When she introduced herself to Ju-Yeon, she mention 28 yo.

In 1999, Eun-Ho age 11, in this year (real) Hae-Ri have the ability to write. Commonly kids develop ability to write letters at 4-6 yo, and write words at 8 yo.

In 2024, Eun Ho age 36 (she mentioned 37 in the show), and (alter) Hae-Ri age is 28 yo. Their age difference is 8 years old. There is not possible in 1999 (real) Hae-Ri is 3 yo can develop ability to write words and describe her feelings.

(alter) Hae-Ri mentioned she have no sibling.
Eun-Ho consciously mention she have little sister.
Both (alter) Hae-Ri and Eun-Ho notice that they are orphan.

My Conclusion.
(alter) Hae-Ri age can be different with (real) Hae-Ri. Because, (alter) Hae-Ri was recreated by Eun-Ho.

(alter) Hae-Ri mentioned she have no sibling and she didn't recognize Eun-Ho are somewhat a proof, she totally a different character. (alter) Hae-Ri character are based on (real) Hae-Ri but not everything.

i dont think i find exact date when Hae-Ri started parking lot job.

But there is scene where Eun-Ho registered to Psychiatrist the 1st time, it show year on it registration form.

And there is scene where Hae-Ri realized about dual identity, but around that time she just believe herself as losing memories rather than having DID. She wrote those experience in her diary, and there is exact date on it.

i mixed (real) Hae-Ri with (alter) Hae-Ri.  I've fixed it.

When (alter) Hae-Ri get along with Ju-Yeon, she mentioned she is an orphan and didnt have any sibling.

Thanks for this reference!!!

I’m not sure it was revealed exactly when she started the parking lot job. How do you know the introductions were the same year, I might’ve missed it? I was thinking since she introduced herself as 25 on her first day and now 28 to Ju yeon, she must’ve started 3 yrs ago, which would then be a year after her break up with Hyuno 4 yrs ago.

 W two worlds Season 2 sc:

Now the timeline is under you responsability, as you can update it!

Haaaa, thank you for this big work. More than one time, I've gave-up on that.

i'll try to update it and make it easier to read. As i'm sure many of us try to find the chronological order of the events.

 W two worlds Season 2 sc:

I can confirm for sure with proof! Episode 3 at 59:08.

She says Hyeri age 25. In 2024 Hyeri is 28, so Parking Job starts in 2021.

You mean when Hae-Ri introduce herself to Kim Min-Yeong (coworker at parking lot)? yes, Hae-Ri said her age is 25 yo. But when Hae-Ri introduced herself to Ju-Yeon, she said her age is 28 yo. So its 3 years different.

Yes i mentioned in additional notes above (and i have edited the order too). But im not sure yet to jump into conclusion that Hae-Ri have work for years in the parking lot.

Another things, around 2019 and 2020, Eun-Ho have broke up with Hyeon-Oh, so nobody notice about the development of (alter) Hae-Ri or Eun-Ho's afternoon activity.

Hae-Ri have worked in those parking lot for about 3 years when she finally get closer to Ju-Yeon right?

It all make sense, but i won't jump there yet.

Okay its confirmed, Eun-Ho have lived as Hae-Ri for years. So yeah, what we W two worlds Season 2 sc  discussed before is correct. Also thanks to jjlew to point it out for me.

Eun-Ho work on parking lot as Hae-Ri around 2021. And (alter) Hae-Ri have existed for around 3 years.

Episode 5 also revealed that Eun-Ho can still remember the early day she pretend to be Hae-Ri.

And another events revealed in episode 5, Eun-Ho's dad and mom died in accident, then her grandma passed away.

Graduation for university student is commonly around age 21-22?

Episode 1-4 gave us many questions.
Although episode 5 didnt give as many answer, but from now on the story and conflict will happen. Some question also will be answered as they release episodes.

oof my bad, i didnt know you havent see ep5 yet.