Research Methodology

City selection: four gates

The overlap dataset uses one shared city list. A city is included only when it passes all four gates:

1. Population / economic weight. Metro area meets a documented population and economic-activity threshold.
2. Time-zone stability. The city has a stable IANA zone, no ongoing zone-boundary dispute, and unambiguous DST rules.
3. Coverage. Every inhabited region is represented; the list is not skewed to any single continent.
4. Registry integrity. The city passes the build-time registry validation (IANA zone resolves, region derives cleanly from country code, no duplicate slugs).

Dataset

The shared dataset backs every overlap study. Row count and format are the same everywhere they're cited because they're read from the same registry entry at build time.

• 24,753 rows of pairwise overlap data.
• 5 published studies derive from this dataset.
• CSV download: /research/overlap-dataset.csv
• Companion repository (verify script + data dictionary): github.com/HaphazardGuess/workday-overlap-dataset

Overlap engine

Overlap is computed by projecting both cities' local working windows onto a shared UTC axis and intersecting the intervals. The engine handles the international dateline explicitly — when a pair's overlap window wraps past 00:00 UTC, both halves are counted, so no pair is silently zeroed out because of wraparound. DST is evaluated per-date, not per-city, so January and July figures reflect the actual clocks in each city.

Studies

• The Remote Work Overlap Report — Across 223 major cities and 24,753 city pairs, the average two cities share about three hours of the 9-to-5 workday — but nearly a third share none of it.
• The Most & Least Connected Cities — A ranking of all 223 major cities by average 9-to-5 overlap with the rest of the world, showing where to base a global team — and where geography makes that impossible.
• How Daylight Saving Breaks Your Calendar — More than a third of city pairs change their workday overlap between January and July — this study measures who gains, who loses, and who never changes their clocks.
• The Meridian Rule — Time-zone overlap is set almost entirely by east–west distance, not total distance — every region has a natural delivery partner on its own meridian.
• Does 9-to-5 Matter? A Window Sensitivity Analysis — Recompute every headline figure across six workday windows. Start time is irrelevant; length is everything — and at ten hours San Francisco's isolation reverses.

Editorial context

Research is subject to Clockjumper's editorial policy. Substantive corrections are logged on the corrections page. Series-specific methodology pages provide the exact code paths and column definitions for each series.

• Workday Overlap Studies — methodology