Career & communication · course 65 of 105

Remote Team Clocks Across Time Zones

Read the clock in someone else’s city: UTC offsets, US and EU daylight-saving dates, the weeks they fall out of step, meetings that land on another day, and the hour both workdays share.

4 modules

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What it teaches

How to read the clock in someone else’s city. UTC and offsets (how far a place’s clock is ahead of or behind the world’s reference clock), the US summer-time dates (second Sunday of March to first Sunday of November) and the EU’s (last Sunday of March to last Sunday of October), converting a time between two named cities on a given date, the weeks each spring and autumn when the US and Europe are out of step (the gap between New York and London is 4 hours instead of 5), the date change (a 4:00 PM Monday meeting in Los Angeles that lands on Tuesday morning in Tokyo), and finding the hour that fits both people’s 9:00-17:00 working day. The AI asks 3 questions, places you, shows a short card per module, then gives you one question at a time.

For remote workers, team leads and anyone who books calls across countries and is tired of getting one hour wrong twice a year. Not a scheduling tool, and it can’t judge your real calendar or whether a country has changed its clocks.

How long

42 items. About 15-25 rounds for someone who already converts times confidently up to about 60-80 for a beginner, plus a 12-item final: 2-3 sessions (estimate, not timed with a real student). The tutor gives a one-line save code at the end of each session.

From the answer key · M1, row C5

It is 2:00 PM on Wednesday 14 January 2026 in Los Angeles. What time is it in Phoenix?

Think first, then show the answer

Answer3:00 PM

WorkingLos Angeles is UTC-8 (standard time), Phoenix is UTC-7 (no summer time): Phoenix is 1 hour ahead of Los Angeles. 2:00 PM + 1 hour = 3:00 PM.

The wrong answer it catches2:00 PM → that’s the July answer, when both are UTC-7; in January Los Angeles is UTC-8 and Phoenix is still UTC-7.

Winter (standard) offsets: New York UTC-5 · Chicago UTC-6 · Denver UTC-7 · Los Angeles UTC-8 · Phoenix UTC-7 all year · London UTC+0 · Paris UTC+1 · Tokyo UTC+9 all year · Kolkata UTC+5:30 all year. The US numbers are the statute’s (15 U.S.C. 261: eastern 5 hours, central 6, mountain 7; Pacific is the fifth zone, UTC-8, checked against the tz database). London’s winter clock is GMT, Greenwich Mean Time, the clock the EU Directive counts in.
Convert: gap = the offset of the city you want minus the offset of the city you have. Add the gap to the time you have. Example: 9:00 AM in Denver on 21 January 2026 (UTC-7, winter) is 4:00 PM in London (UTC+0): the gap is +7 hours.

The modules

4 modules, drilled one item at a time.

M0
The rules
The rules: UTC, the US and EU summer-time dates, how far clocks move, zone names, the date line
M1
Converting a time between two cities
Convert a time between two cities, and give a city’s offset from UTC
M2
Out-of-step weeks and the date line
The US and EU change-over dates, the out-of-step weeks, and the date change across the date line
M3
Finding the shared hours
Find the 9:00-17:00 window two cities share, how many shared hours there are, and a meeting start that fits both

Before it teaches, it asks

1
What do you use time zones for (meetings with another country, a remote team, travel, nothing yet), and which cities are involved?
2
It is 9:00 AM on Wednesday 15 July 2026 in New York. What time is it in Tokyo?
3
On what date does summer time start in the US in 2026? (The clocks change on a Sunday.)

What’s exact, and what isn’t

Show

Straight from the course’s own notes.

The rules are quoted: From the saved pages, read 2026-10-12: the US statute 15 U.S.C. 260a, 261 and 263 (Government Publishing Office, U.S. Code 2024 edition), EU Directive 2000/84/EC Articles 1-3, the IANA Time Zone Database pages (zone-name format) and NOAA’s date-line page. A script fails if any saved page changes or any quote is not word for word on its page. It does not re-fetch live pages.
Directive text: EUR-Lex (the official source) answers scripts with an empty challenge page, so the Directive is quoted from two separate text copies (a 2001 post in the IANA tz mailing-list archive and lexploria.com); a script checks that both carry each quoted sentence. The as-adopted PDF on legislation.gov.uk (OJ L 31, 2.2.2001, p. 21) has a text layer in custom glyph names; decoded, it carries Articles 1-3 word for word (Article 1 has single quotation marks).
Computed by script: Every M1, M2 and M3 key and every number in the Workings. Each key is worked out twice and the two must agree: once by Python’s zoneinfo (tz database 2026c) and once by a script’s own offsets and the two quoted rules. A script also checks that the tz database changes clocks on exactly the quoted Sundays for 2025-2030, and that the US goes first in spring and the EU first in autumn in every year 2007-2099. All 31 wrong-answer rows are proven wrong and proven to be the slip they name. M0's Answers are written from the quoted rules, not computed.
Chosen to avoid change: The tz database’s 2026 release notes (2026b to 2026e, read 2026-10-12) record British Columbia, Alberta, the Northwest Territories and Manitoba going to permanent time and Morocco to permanent +00, so the course uses none of those places. The 11 cities are New York, Chicago, Denver, Los Angeles, Phoenix, Honolulu, London, Paris, Tokyo, Kolkata and Sydney.
Honest limits: London changes on the EU’s dates in the tz database (script-checked), but the Directive is quoted for Member States only and the course does not quote UK law. Sydney’s summer time is not quoted anywhere; Sydney is only asked inside the stretch where the tz database has it at UTC+10. The course drills the rules as quoted; it can’t say whether any government has changed them since, and it is not legal, travel or scheduling advice. Most items use 2026 dates, with 2027 for a few rule dates.
Not in it yet: Other cities and countries, Southern-hemisphere summer-time rules, three-way overlaps, meeting-fairness (whose turn to take the awkward hour), working days other than 9:00-17:00, Canadian zones.