Now in TestFlight beta
Sleep when your body wants to.
Arrive ready to work.
Circa is the circadian app that runs the whole jet-lag plan, not just light and melatonin. One flight number generates an hour-by-hour plan that flexes around your real schedule.
- First plan free, no time limit
- HK$149 a year for unlimited trips
- Built on a real, unit-tested engine
LHR → HKG · BA 27
Day 1, Hong Kong
- 14:30 06:30 Bright daylight, 30 min Core
- 15:30 07:30 Light meal, protein Supportive
- 17:00 09:00 Last caffeine of the day Core
- 18:30 10:30 30-min easy walk Supportive
- 20:00 12:00 Dinner, then no food Supportive
- 21:00 13:00 Dim the room Core
- 21:30 13:30 0.5 mg melatonin Core
- 22:30 14:30 Sleep window opens Core
Built on real circadian science
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648
Plans tested
108 routes × 6 profiles, 100% correct
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82
Unit tests
JS engine, all passing
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8 levers
In every plan
Light, sleep, caffeine, melatonin, exercise, food, hydration, transit
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0
Pseudoscience tolerated
Evidence-graded recommendations
The cost you are paying
Jet lag is not just being tired. It is a week of being worse.
The body clock shifts roughly half an hour to an hour a day on its own. The first three days of a trip are when most travellers think jet lag lives. The next six are when most of the productivity cost actually shows up, because the person feels approximately functional and is therefore not protecting themselves.
- 0.5-1 hr/day
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How fast your body adjusts unaided
The rule of thumb is one day per time zone. A New York to Hong Kong flight is twelve time zones. Twelve days, each way.
- 61%
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How well a jet-lagged person performs
Industry estimates of productivity during the recovery window. Every jet-lagged day is a sub-standard day, for a week or more.
- 3-5 days
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Each direction of a long-haul trip
For a round trip, that is six to ten productive days lost. Most travellers absorb it as background; it is not.
How it works
One flight number. A full plan. Built on real science.
The protocol is the same one researchers use for shift workers and astronauts. The adaptation is what makes it usable for a Tuesday in Tokyo.
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Type one flight number and a date. Circa pulls the real route, times, and time zones from the flight data layer. No manual gymnastics.
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When is your first meeting? When do you exercise? Take melatonin? Drink alcohol? Two minutes, one screen. The plan adapts to all of it.
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Light, sleep, caffeine, melatonin, exercise, food, hydration, supplements, transit, alcohol mitigation. Every recommendation explains why when you tap it.
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A 60-second handoff card for the cabin staff: when to dim, when to wake you, when to skip the meal service. The most underrated travel hack we ship.
The whole-trip difference
The complete protocol, not the first half of it.
Every jet-lag app covers light and melatonin, the levers everyone agrees on. The science also supports exercise, meal timing, hydration, and a handful of supportive practices. Circa runs all of them. The others do not.
| What the plan covers | Circa | Timeshifter | StopJetLag | Flykitt |
|---|---|---|---|---|
| Light, timed both directions | Yes | Yes | Yes | Yes |
| Sleep, including on the plane | Yes | Yes | Yes | Partial |
| Caffeine, dose-timed for direction | Yes | Yes | Yes | No |
| Low-dose melatonin, phase-anchored | Yes | Yes | Yes | Yes |
| Exercise as a zeitgeber | Yes | No | Yes | No |
| Meal timing + content | Yes | No | Partial | No |
| Hydration + electrolytes | Yes | No | No | No |
| Transit, alcohol, illness-prevention | Yes | No | No | No |
| Personalised to your wake time + meetings | Yes | Partial | Partial | Partial |
| Cabin-crew brief, ready to hand off | Yes | No | No | No |
| Round-trip and multi-leg planning | Yes | Partial | No | Partial |
| Evidence-graded recommendations | Yes | Partial | No | No |
| Requires buying a physical kit | No | No | No | Yes |
| Annual price | HK$149 / ~US$19 | HK$198 / ~US$25 | HK$610 / ~US$78 per plan | HK$770 / ~US$99 kit |
Competitor data current as of June 2026. Levers and features compared from public sources and competitive teardowns. Where we mark “partial,” the lever exists but is generic or applied without timing. We will keep this honest as competitors evolve.
The eight levers
Every lever the science supports. Graded honestly.
Settled science is tagged Core. Well-evidenced but more modest effects are tagged Supportive. Environment and comfort moves are tagged Comfort. No overclaiming, anywhere.
- Core
Light, timed in both directions
Bright light at the right hour of your biological day advances or delays your clock by an hour or more. Wrong time, it does the opposite. Direction matters; Circa handles it.
- Core
Sleep, including on the plane
A two-process model decides when sleep is biologically available. Circa knows when to sleep aloft to protect your destination night, and when staying awake is the right move.
- Core
Caffeine, cut at the right hour
Caffeine has a five-to-six hour half-life. Mistimed, it sabotages the sleep window you are trying to protect. Circa schedules your last cup against the right reference.
- Core
Low-dose melatonin, phase-anchored
0.3 to 1 mg taken at the right destination hour shifts the clock. Mistimed, it does nothing or backfires. Melatonin is a chronobiotic, not a sleeping pill.
- Supportive
Exercise, the underused zeitgeber
Movement at the right time of the destination day reinforces the rest of the protocol. Placed wrong, it confuses the signal. Circa places it relative to your real schedule.
- Supportive
Meals, on destination time
Peripheral oscillators in the gut and liver respond to meal timing. Circa schedules destination-zone meals in flight, not after arrival.
- Supportive
Hydration and electrolytes
A long-haul flight can cost two to three litres of fluid. The dehydration alone produces fatigue that looks like jet lag and stacks on top of it.
- Comfort
Transit, alcohol, illness-prevention
When to mask, when to cut alcohol, what to ask the cabin crew, when a lounge shower beats a hotel nap. Every plan covers the real-world stuff most apps ignore.
Pricing
Cheaper than one airport coffee, per trip.
The annual is HK$149 a year, less than Timeshifter and a fraction of StopJetLag or Flykitt. The first plan is free, forever. The per-trip credit covers the traveller who flies only once or twice a year. There is no lifetime tier and no monthly grift.
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First plan
Free
Try Circa for the next trip you have.
Start with a free plan- One complete trip plan
- Light, sleep, caffeine, melatonin
- Personalised to your wake time
- Cabin-crew brief
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Per-trip credit
HK$38
For travellers who fly once or twice a year.
Buy a credit- One full premium plan
- Every lever Circa runs
- Exercise, food, hydration, supplements
- Round-trip support
- No subscription
- Recommended
Annual
HK$149
Recommended for 3+ trips a year. Pays for itself in one trip.
Get early access- Unlimited trip plans
- Every lever, every trip
- Full readiness curve
- Round-trip + multi-leg
- Cabin brief, pill-detail rationale
- Notifications + Live Activity
Subscriptions are processed through Apple. Apple takes the standard platform fee. You can cancel any time from the App Store. Prices may vary slightly by storefront. The exact price shown at checkout is the price you pay.
Early access
Get on the list. We invite in waves.
First plan free, always. Founding-member pricing available when invitations open.
We only email you about Circa. Unsubscribe any time. See our privacy policy.
Common questions
Quick answers, before you commit.
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How is Circa different from Timeshifter?
Timeshifter is excellent at light and melatonin. Circa runs the whole protocol: exercise placement, meal timing, hydration, supplements, transit, illness-prevention, alcohol mitigation. The lever stack we own is the differentiator, and most of our early users come from Timeshifter and keep both before settling on Circa.
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Is the first plan really free?
Yes. The first plan is free, forever, with no time limit. The annual is HK$149 for unlimited trips. The per-trip credit is HK$38 for one trip.
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Does Circa work for round trips?
Yes. The engine treats the return as part of the same trip and carries the phase state. The homebound plan accounts for where your body clock actually is when you land, not where it started.
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When is Circa launching?
Circa is in TestFlight beta. Get on the waitlist and you will be invited in a wave before the public App Store launch later this year.
See all questions on the FAQ page.
Coming to the App Store
Plan your next trip with Circa.
First plan free. HK$149 a year for unlimited trips, or HK$38 per trip.