Study 5 of 5
Does 9-to-5 Matter? A Window Sensitivity Analysis
We recomputed every headline figure across six different workday windows. Two findings stand out: start time is irrelevant, and at ten hours the least-connected city in the world flips.
Last updated July 2026
ClockJumper studies are produced with AI assistance and human review. · research methodology
1 · Start time doesn't matter
The three eight-hour windows — 8:00–16:00, 9:00–17:00 and 10:00–18:00 — produce identical results for every one of the 223 cities. The reason is arithmetic: overlap depends only on the offset difference between two cities and the length of the window, so shifting both cities' workdays by the same number of hours cancels out and every pair keeps the same shared time.
| Window | Length | Jan mean | Zero-overlap | SF reach | HNL reach | Gap (HNL − SF) |
|---|---|---|---|---|---|---|
| 8:00–16:00 | 8h | 3h04m | 29.5% | 73 | 117 | +44 |
| 9:00–17:00 | 8h | 3h04m | 29.5% | 73 | 117 | +44 |
| 10:00–18:00 | 8h | 3h04m | 29.5% | 73 | 117 | +44 |
| 8:00–17:00 | 9h | 3h50m | 21.9% | 123 | 128 | +5 |
| 9:00–18:00 | 9h | 3h50m | 21.9% | 123 | 128 | +5 |
| 8:00–18:00 | 10h | 4h40m | 16.5% | 174 | 135 | -39 |
Reach columns count how many of the other 222 cities each place shares any working minute with in January or July.
2 · Length is everything
As the day extends from eight to nine to ten hours, the average pair's shared workday climbs — 3h04m → 3h50m → 4h40m — and the share of pairs with no overlap at all falls in step: 29.5% → 21.9% → 16.5%. Two extra hours of workday redeem roughly 3,207 pairs from the zero column — mostly cities that miss a live connection to the next continent by minutes rather than by continents.
3 · The reversal
The Most & Least Connected Cities study found San Francisco sitting inside a six-way Pacific-coast tie at the bottom of the reach ranking: at an eight-hour workday it touches only 73 of 222 other cities, while Honolulu — mid-Pacific, straddling the dateline — reaches 117. Extend the day to nine hours and the gap nearly closes (123 vs 128). Extend it to ten and the ranking flips outright: San Francisco jumps to 174, while Honolulu climbs only to 135 — enough to drop it into the bottom three cities globally.
The mechanism is the shape of each city's connections. Honolulu's reach is wide but shallow — many one- and two-hour slivers with Asian mornings on one side and American afternoons on the other, most of which exist at any window length because a small overlap is still an overlap. San Francisco's reach is deep or nothing: its links to Europe and Asia sit just outside an eight-hour window, waiting to enter reach as soon as the workday grows. When it does, whole continents crash in at once.
Put simply: Honolulu's connectivity is broad and low-margin; San Francisco's is a threshold effect. The 9-to-5 frame catches Honolulu's slivers and misses San Francisco's next tier by a few minutes on the clock.
4 · What this means for the other studies
The headline finding of the Most & Least Connected Cities study — that San Francisco is tied for the lowest reach on Earth — holds for any eight-hour workday regardless of start time, and reverses only when the day is extended to ten hours. Every other figure on the research hub uses the 9:00–17:00 / eight-hour frame; the results published in the Remote Work Overlap Report, Most & Least Connected Cities, How Daylight Saving Breaks Your Calendar and The Meridian Rule studies are all invariant under any 8-hour start-time choice.
Figures: computed from the 24,753-pair overlap dataset for six workday windows; January 2026 sample for the mean and zero-overlap columns, January and July 2026 for reach.
- Why does the site use 9-to-5?
- It is the most widely-recognised office-hours convention and the default across our converter, hub pages, and headline dataset. This study measures what changes if you use a different eight-, nine-, or ten-hour window instead.
- Does the San Francisco finding depend on the 9-to-5 assumption?
- Only on the eight-hour length, not the start time. San Francisco is the least-reaching city under any eight-hour window — 8:00–16:00, 9:00–17:00 and 10:00–18:00 all give it a reach of 73. Extend the day to ten hours and the finding reverses: San Francisco jumps to 174 while Honolulu drops toward the bottom of the ranking.
- Why do the three 8-hour windows produce identical results?
- Overlap depends only on the offset difference between two cities and the length of the window. Shifting both cities’ workdays by the same number of hours cancels out — every pair keeps the same overlap.
Explore the live data
The numbers on this page are a static snapshot. Use the live tools below to check the current offset, overlap, and daylight-saving status for any city or pair.
Sources
- ClockJumper Global Workday Overlap Dataset (2026) — 24,753 city pairs across 223 cities, recomputed here across six window lengths.
- IANA Time Zone Database — UTC offsets sampled on 2026-01-15 and 2026-07-15.
- Full inclusion criteria and computation notes: Overlap Studies methodology.