Early in the morning, I open a public post from Tibo.
It starts with a rickroll, out of nowhere. Then it gets to the point: usage limits are being reset globally. And then comes the line that wakes my brain up instantly:
"today around 6 PM PST." [1]
My English is fine. That's not the problem.
The problem is: what time is that in Japan?
Short answer: in September 2026, if it means local time on the U.S. West Coast, 6 PM is around 10 AM the next morning in Japan. September falls inside daylight saving time, so Pacific time is actually PDT, which is UTC−7. [2][3]
If you take "PST" literally as UTC−8, you get 11 AM. But if the post means "6 PM on the clock out West that day," the calendar says PDT, so 10 AM is the real target.
And the reset time wasn't the only thing I picked up from this.
I learned daylight saving time too. Tibo gave me a lesson.
1. The answer: 6 PM Pacific in September is 10 AM the next day in Japan
Japan Standard Time is UTC+9.
U.S. Pacific time comes in two flavors, depending on the season. [2]
| Pacific time | UTC offset | Difference from Japan | 6 PM becomes |
|---|---|---|---|
| PDT (daylight time) | UTC−7 | Japan is 16 hours ahead | 10 AM next day |
| PST (standard time) | UTC−8 | Japan is 17 hours ahead | 11 AM next day |
In 2026, U.S. daylight saving time runs from 2 AM on March 8 to 2 AM on November 1, local time. [3]
So September is PDT territory.
Tibo's post showed up in Japan early on September 8, but on the Pacific coast it was still September 7. Read "today around 6 PM" as Pacific local time and you get about 6 PM PDT on September 7 → about 10 AM JST on September 8.
It says "around," so don't expect the whole world to light up at exactly 10:00:00. Think of it as roughly 10.
Still, it's a perfectly good time to set an alarm.
2. Why does the gap change by an hour between summer and winter?
Blame daylight saving time.
In spring, clocks jump forward one hour. In fall, they go back one hour. [3]
Put very roughly, the idea is to move an hour of daylight from the morning to the evening, so the part of the day when people are out and about stays bright longer. NIST puts it this way: during daylight saving time, morning light starts an hour later and evening light lasts an hour longer. [2]
So Pacific time is:
- Winter: PST = UTC−8
- Summer: PDT = UTC−7
Japan stays on JST = UTC+9 and generally doesn't change its clocks.
That makes the gap with Japan:
- Winter: 17 hours
- Summer: 16 hours
In summer, the American clock slides one hour closer to Japan.
That's all you really need to remember.
3. Quick conversion: just add 16 in summer, 17 in winter
The by-the-book way is to go through UTC.
Take 6 PM PDT. It's UTC−7, so add 7 hours and you get 1 AM UTC the next day. Then add 9 hours for Japan's UTC+9 and you land on 10 AM.
Correct.
But doing that in your head every time is a pain.
In practice:
Pacific time → Japan time
- Daylight time: +16 hours
- Standard time: +17 hours
That's it.
6 PM + 16 hours = 10 AM the next morning.
One step. Done.
4. An even faster trick: flip AM/PM, then add 4 in summer, 5 in winter
If even adding 16 feels like too much work, you can get lazier.
When converting Pacific time to Japan time, first flip AM and PM.
6 PM becomes 6 AM.
Then:
- Summer: +4 hours → 10 AM
- Winter: +5 hours → 11 AM
Why does this work? Flipping AM and PM is basically the same as adding 12 hours.
The summer gap of 16 hours = 12 + 4.
The winter gap of 17 hours = 12 + 5.
So the rule in your head is:
See Pacific time? Flip AM/PM. Add 4 in summer, 5 in winter.
That's all.
At this point it's less of a time zone calculation and more of a button combo.
5. It says "PST," so why read it as PDT in September?
This is the biggest trap.
PST is Pacific Standard Time, UTC−8.
PDT is Pacific Daylight Time, UTC−7. [2]
NIST explains that West Coast time is called PST or PDT depending on the season, and that if you want to refer to local time all year round, you can write PT (Pacific Time). [2]
So if someone means "6 PM local time on the West Coast" in September, PDT is technically the right label.
But in everyday posts, a lot of people use "PST" loosely to mean "West Coast time."
So the safe approach has two steps:
- If you read the label literally, PST = UTC−8.
- If it means the local clock over there, check whether that date falls in daylight saving time.
For a September announcement like this one, that gives you: 10 AM is the best bet, 11 AM if you read PST literally.
6. School-level time zones suddenly matter when you're waiting on tokens
Most people know there's a time difference between Japan and the U.S. But not many can see "PST" or "PDT" and instantly know which one applies right now.
In school it ends with "Japan and America are in different time zones." Online, it suddenly turns into this:
"6 PM PST. So what time do I need to get up?"
That's when daylight saving time barges into your life.
And it doesn't come through an international conference or a business trip.
It comes through waiting for an AI usage reset.
As a geography lesson, it's pretty unorthodox. But it sticks.
Memorizing "PDT is UTC−7" won't do much.
"When Tibo says 6 PM in summer, it's 10 AM the next morning in Japan"
hits a lot harder.
7. Pavlov's dog learned time zones
By now, the habit loop is complete.
Tibo hints at a reset.
↓
Check the time.
↓
Figure out if it's summer or winter time.
↓
Convert to Japan time.
↓
Set an alarm.
↓
Wake up and fire up Codex.
↓
Go back to sleep.
I'm not claiming this is scientifically proven classical conditioning. It's just a joke.
But it sure looks like Pavlov's dog.
Instead of a bell: "6 PM PST."
Instead of food: a usage reset.
And in the end, what the dog learned wasn't drooling on cue. It was North American daylight saving time.
8. Beyond 6 PM: this one table covers most cases
For converting West Coast evening announcements to Japan time, this covers the range you'll probably need.
| Pacific local time | Japan time in summer (PDT) | Japan time in winter (PST) |
|---|---|---|
| 3 PM | 7 AM next day | 8 AM next day |
| 4 PM | 8 AM next day | 9 AM next day |
| 5 PM | 9 AM next day | 10 AM next day |
| 6 PM | 10 AM next day | 11 AM next day |
| 7 PM | 11 AM next day | noon next day |
| 8 PM | noon next day | 1 PM next day |
Around the spring and fall switchover dates, don't just assume 16 or 17. Check the date.
In 2026, daylight saving time runs from March 8 to November 1. [3]
Wrap-up: I was waiting on a Tibo reset and somehow took a class on daylight saving time
It all started with "What time is 6 PM PST in Japan?"
The answer, reading it as Pacific local time in September 2026: around 10 AM the next morning.
From there, everything clicked:
- PST is winter time, UTC−8
- PDT is summer time, UTC−7
- Japan is 17 hours ahead in winter, 16 in summer
- The gap shrinks because clocks jump forward an hour in spring
- Mental shortcut: "flip AM/PM → +4 in summer, +5 in winter"
All I was doing was chasing an AI reset, and now North American time zones are stuck in my head.
Stuff that never stuck in school finally sticks while you're waiting on tokens.
You never know where your education will come from.
This time, it came from Tibo.
References (3)
- Tibo (@thsottiaux), öffentlicher Post auf X, Status 2097043464538264003, angezeigt am 8. September 2026 (japanische Zeit) x.com
- National Institute of Standards and Technology (NIST), „Local Time FAQs“ nist.gov
- National Institute of Standards and Technology (NIST), „Daylight Saving Time Rules“. Regel für 2026: 8. März, 2 Uhr Ortszeit, bis 1. November, 2 Uhr Ortszeit nist.gov
