"What's the best time to call?" is one of the most common questions in international business, remote work, and global family life. The answer depends on three factors: the time difference between the two cities, whether either city observes Daylight Saving Time, and what counts as "business hours" or "reasonable hours" in each location.
This guide provides data-driven recommendations for 20 major city pairs, including the optimal call windows, the windows to avoid, and a difficulty rating based on how much business-hours overlap exists. All times are shown in standard (winter) time unless noted.
How to Use This Guide
Each entry shows the best window (when both cities are in business hours or at least reasonable waking hours), the window to avoid (when one city is outside working hours), and a difficulty rating from 1–5 stars based on the amount of business-hours overlap:
- ★★★★★ (5) — 5+ hours of business-hours overlap. Easy to schedule.
- ★★★★☆ (4) — 3–4 hours of overlap. Good morning or afternoon window.
- ★★★☆☆ (3) — 1–2 hours of overlap. Requires discipline to hit the window.
- ★★☆☆☆ (2) — Less than 1 hour of overlap. Early morning or late evening required.
- ★☆☆☆☆ (1) — No business-hours overlap. Async communication recommended.
Best Call Windows by City Pair
| City Pair | Best Window | Rating |
|---|---|---|
New York → London −5h (winter) / −4h (summer) | 9am–12pm ET / 2pm–5pm GMT | ★★★★☆ |
New York → Paris −6h (winter) / −5h (summer) | 9am–11am ET / 3pm–5pm CET | ★★★☆☆ |
New York → Dubai −9h (winter) / −8h (summer) | 8am–9am ET / 5pm–6pm GST | ★★☆☆☆ |
New York → Singapore −13h (winter) / −12h (summer) | 8am–9am ET / 9pm–10pm SGT | ★☆☆☆☆ |
New York → Tokyo −14h (winter) / −13h (summer) | 7am–8am ET / 9pm–10pm JST | ★☆☆☆☆ |
London → Singapore +8h | 9am–1pm GMT / 5pm–9pm SGT | ★★★☆☆ |
London → Sydney +10h to +11h | 8am–9am GMT / 6pm–7pm AEDT | ★☆☆☆☆ |
London → Dubai +4h | 9am–5pm GMT / 1pm–9pm GST | ★★★★★ |
Dubai → Singapore +4h | 9am–5pm GST / 1pm–9pm SGT | ★★★★★ |
Los Angeles → New York −3h | 9am–2pm PT / 12pm–5pm ET | ★★★★★ |
Los Angeles → Tokyo −17h (winter) / −16h (summer) | 4pm–5pm PT / 9am–10am JST | ★★☆☆☆ |
Singapore → Sydney +2h to +3h | 9am–3pm SGT / 11am–5pm AEDT | ★★★★☆ |
Toronto → London −5h (winter) / −4h (summer) | 9am–12pm ET / 2pm–5pm GMT | ★★★★☆ |
Berlin → Singapore +7h | 9am–1pm CET / 4pm–8pm SGT | ★★★☆☆ |
Mumbai → London +5:30h | 11:30am–5pm IST / 6am–11:30am GMT | ★★★★☆ |
São Paulo → New York +2h (winter) / +1h (summer) | 9am–3pm BRT / 7am–1pm ET | ★★★★☆ |
Tokyo → Sydney +1h to +2h | 9am–5pm JST / 10am–6pm AEDT | ★★★★★ |
Chicago → London −6h (winter) / −5h (summer) | 8am–11am CT / 2pm–5pm GMT | ★★★☆☆ |
Hong Kong → London +8h | 9am–1pm HKT / 1am–5am GMT | ★☆☆☆☆ |
Paris → Dubai +3h | 9am–2pm CET / 12pm–5pm GST | ★★★★☆ |
The Hardest Pairs: Trans-Pacific Calls
New York–Tokyo: 14 Hours Apart
The most challenging city pairs are those that span the Pacific Ocean. New York to Tokyo (14 hours apart) and New York to Singapore (13 hours apart) have zero business-hours overlap. When it's 9am in New York, it's 11pm in Tokyo. The only viable windows require someone to be at work very early or very late.
For teams that regularly need to collaborate across these gaps, the most sustainable approaches are:
- Async-first workflow — recorded video updates, detailed written briefs, shared documents with comments
- Rotating the inconvenient slot — alternate who takes the early morning or late evening call
- Overlap days — schedule live collaboration during quarterly offsites when teams are in the same location
- Handoff model — structure work so one team hands off to the other at end of day, enabling a "follow the sun" workflow
The Easiest Pairs: Same-Region Calls
The easiest city pairs are those within the same region or with small time differences. Dubai–Singapore (4 hours apart), Tokyo–Sydney (1–2 hours apart), and London–Dubai (4 hours apart) all offer 5+ hours of business-hours overlap, making scheduling trivial.
Within the Americas, Los Angeles to New York (3 hours) is one of the most commonly scheduled pairs and offers a comfortable 5-hour overlap window. The main consideration is that New York's business day starts 3 hours before Los Angeles, so early-morning East Coast calls require West Coast participants to join before 9am local time.
How DST Shifts These Windows
The Spring Forward / Fall Back Gap
All windows above are shown in standard (winter) time. During Daylight Saving Time, the offsets change — and because different regions transition on different dates, the windows shift temporarily during the transition weeks.
USA–Europe Transition Weeks
The most commonly affected pairs are those between the USA/Canada and Europe. During the 2–3 weeks when the USA has sprung forward but Europe hasn't (mid-March), or when Europe has fallen back but the USA hasn't (late October), the time difference is one hour different from its usual value. Always verify the current offset before scheduling during these periods.
Use our Timezone Converter to check the current, real-time offset between any two cities, accounting for live DST status.
Check Current Times Before You Call
Compare Two Cities Side by Side
For any specific pair, our Compare tool shows both cities' current times, timezones, and weather side by side. Check the most popular pairs: