# Core hours: choosing meeting windows a distributed team can live with

*August 15, 2026 · Charles Brun · Playbook · Everest Blog*

> The four-hour overlap rule everyone repeats has no research behind it. Here is what the evidence actually says, and how to set core hours from your real overlap instead.

Search for how much overlap a distributed team needs and you will be told four hours. Sometimes two
to four, sometimes four to six, always with the confidence of a settled fact.

It is not one. There is no study behind that number. It appears in blog posts that cite other blog
posts, and — this is the part that should end the argument — none of the companies most associated
with distributed work publish a required overlap at all. GitLab's handbook, which documents almost
everything, does not name a figure.

So if you are setting core hours for a team, you are not implementing a known best practice. You are
making a judgement call. It is worth making it from the evidence that does exist.

## What the research actually found

The most useful study here is Chauvin, Choudhury and Fang's *Working Around the Clock*
([Organization Science, 2024](https://researchonline.lse.ac.uk/id/eprint/128758/)). It tracked
12,038 employees across 167 cities inside one multinational, and used daylight-saving transitions as
a natural experiment — when clocks move, the overlap between two colleagues changes while nothing
else about them does.

The headline: **a roughly one-hour increase in time zone separation reduced synchronous
communication by about 11%.**

The interesting part is how small that is. The clock shift removed 19.3% of the average pair's
overlap — 1.1 hours from a mean of 5.7 — but synchronous contact fell by only 11%. The conversations
did not disappear. People moved them outside their own working hours.

Two findings from the same paper are worth sitting with:

- **The cost lands unevenly.** Employees with two hours or less of overlap with their manager did
  24.6% of their communication outside business hours, against 11.9% for those with full overlap.
  The share was 9% in countries with a 35–39 hour statutory limit on the working week, and 32% in
  countries with no legal limit.
- **Asynchronous communication did not rise to compensate.** The effect on async volume was
  statistically indistinguishable from zero.

That last one deserves attention, because it cuts against the comfortable story. Distance did not
make this organisation more asynchronous. It made people work in the evening. Async is a practice a
team adopts deliberately; it does not appear on its own when the overlap shrinks.

**The caveats, stated plainly:** this is one US-headquartered multinational in natural resource
extraction, observed over twelve weeks in 2017, in a culture where 85% of communication was
synchronous. It is not a study of remote-first startups. It is, however, a real causal estimate,
which is more than any of the "four hours" advice can claim.

## Set core hours from your actual overlap

The practical implication is not a number to copy. It is a method.

1. **Compute the real overlap for each pair of locations.** Not for the team as a whole — the
   whole-team overlap is often zero, and that fact should not stop two of your people talking.
2. **Name the window that survives.** For a London–Bengaluru team, working days genuinely overlap
   between about 09:00 and 12:30 UTC. That is your core window: the hours where live conversation is
   legitimate without anyone making a sacrifice.
3. **Declare everything outside it async by default.** Not forbidden — async by default, so that
   booking outside the window is a decision someone has to justify rather than an accident.
4. **Write down the hours that are nobody's.** A core window implies quiet hours. The teams where
   this works are the ones where the quiet hours are as explicit as the core ones.

If the whole-team window is empty, you are not doing it wrong — that is the ordinary result once a
team has three hops. What to do about it is the subject of
[how to schedule meetings across time zones](/blog/schedule-meetings-across-time-zones/).

## What the practitioners actually publish

Since the four-hour rule has no source, it is worth reading what the companies with the longest
distributed track records really say. GitLab's
[all-remote handbook](https://handbook.gitlab.com/handbook/company/culture/all-remote/meetings/)
is the most operational, and its advice is structural rather than numeric:

- Create meetings that overlap between EMEA/APAC, APAC/AMER and AMER/EMEA — pairs, not the whole
  company.
- Nominate volunteers to host in the time zones the meeting suits.
- Record group meetings that cross zones so people can participate asynchronously.
- Attach a live agenda doc to every invite, shared at least 24 hours ahead, ideally 72.
- Run 25 and 50-minute meetings rather than 30 and 60.

Doist states that async is the default and that meetings are rare, putting its own async share at
95% — a self-reported figure from a company that sells an async communication product, so treat it
as a statement of practice rather than a benchmark. Zapier has described alternating meeting times
so the same people are not always inconvenienced.

Notice what none of them provide: a minimum overlap. The advice that survives contact with practice
is about pairing, rotating, recording and documenting — not about a threshold.

## The agenda rule does more work than the hours

If you adopt one thing from that list, make it the agenda attached to the invite, shared in advance.

Across time zones it does something it cannot do in a co-located office: it lets someone who cannot
attend contribute before the meeting and read the outcome afterwards, which converts a meeting they
would have lost sleep for into one they can skip. A recurring call with no agenda cannot be skipped
safely, so everyone attends everything, at whatever hour it lands.

This is also the cheapest test of whether a meeting needed to be live. If nobody can write down what
the meeting is for, that is information about the meeting.

## Claims worth not repeating

This subject has an unusually high density of numbers that dissolve when you follow them back.
Each of these is repeated constantly, and each is wrong or unsupported:

| The claim | What it actually is |
| --- | --- |
| "Teams need four hours of overlap" | No study. Blog posts citing blog posts; none of the major all-remote companies publish a figure |
| "Science says the best meeting time is Tuesday 2:30 p.m." | Booking-rate telemetry from a scheduling vendor, not research — and meaningless across zones, since it is Wednesday morning in Sydney |
| "Meetings waste $37 billion a year" | Traces to a 1989 magazine article whose sources cannot be reconstructed |
| "Employees waste 31 hours a month in unproductive meetings" | Traces to a 1998 study which found the opposite — that most meetings were rated at least somewhat productive |
| "Cutting meetings 40% raises productivity 71%" | A survey of 76 companies that had already chosen to adopt no-meeting days, self-reported, no control group |

The pattern is the same each time: a vendor metric or an old survey, promoted to a law, then cited
by everyone who needs a statistic. You do not need any of them to justify protecting your team's
evenings.

One real number is worth more than five invented ones: **30% of meetings now span multiple time
zones**, up about eight percentage points since 2021, according to
[Microsoft's telemetry](https://www.microsoft.com/en-us/worklab/work-trend-index/breaking-down-infinite-workday)
from its own 365 customers. Caveat included: that is a vendor measuring its own users, with European
Union and education tenants excluded.

## Five lines, then leave it alone

Core hours fail when they are a document nobody can recite. Keep it to something a new joiner can
absorb in a minute:

1. The core window, named in UTC and in each city's local time — and re-checked after each clock
   change, because [the offset between two cities is not a constant](/blog/recurring-meeting-daylight-saving-drift/).
2. The quiet hours nobody books.
3. What happens when a meeting has to fall outside the window — who decides, and whose turn it is.
4. The agenda rule: no agenda 24 hours ahead, no meeting.
5. What async default means in practice: which decisions can be made in writing.

Then place them. Choosing which hours inside the window go to focused work and which to coordination
is the same problem every calendar has, distributed or not — and it is covered in
[maker's schedule vs. manager's schedule](/blog/makers-schedule-vs-managers-schedule/) and
[planning your week](/blog/weekly-planning-calendar-guide/).

The thing to hold on to is the finding underneath all of it. Shrinking the overlap does not shrink
the amount of talking a team needs to do. It just moves that talking into somebody's evening — and,
on the evidence, into the evenings of the people least able to object.

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