Best Time to Call Someone in Another Country

8 min read

Calling someone internationally sounds simple until you realize it is 3 AM where they are. Finding a time that works for both sides requires knowing the UTC offset for each location, whether Daylight Saving Time is currently active, and what counts as reasonable hours for the person you are calling. This guide walks through the process and gives you ready-made overlap windows for the most common country pairs.

The golden rule: think in UTC first

The easiest way to find a good call time is to stop thinking in local times and start thinking in UTC. Convert both people’s available hours to UTC, find the overlap, then convert back to local time for each person.

For example, if you are in London (UTC+1 in summer) and want to call someone in Toronto (UTC−4 in summer), your working hours of 9 AM–6 PM London time translate to 8:00–17:00 UTC. Toronto’s 9 AM–6 PM translates to 13:00–22:00 UTC. The overlap is 13:00–17:00 UTC — which is 2–6 PM in London and 9 AM–1 PM in Toronto. That’s a comfortable four-hour window.

What counts as a reasonable call time?

This depends on the relationship and the purpose of the call:

Business calls: 9 AM–6 PM local time for the recipient. Never call before 9 AM or after 6 PM for professional matters unless agreed in advance.
Personal calls to family or friends: 8 AM–9 PM is generally acceptable. Most people are awake and not yet in bed.
Urgent calls: Any time, but send a text or message first so they know to expect it.
Video calls with teams: Aim for 10 AM–4 PM in all locations if possible — avoids the early-morning and post-work fatigue that affects meeting quality.

Ready-made windows for common country pairs

These windows assume standard business hours (9 AM–6 PM) for both sides and use standard time offsets (not DST). Check current DST status before scheduling.

USA (New York) ↔ United Kingdom (London)

London is 5 hours ahead in winter, 4 hours ahead in summer

Best window: 9 AM–1 PM New York / 2–6 PM London (winter) or 9 AM–2 PM NY / 1–6 PM London (summer)

Good overlap — mornings in New York align with afternoons in London.

USA (New York) ↔ India (Mumbai)

Mumbai is 10.5 hours ahead

Best window: 8–9:30 AM New York / 6:30–8 PM Mumbai

Very tight overlap. Early morning NY / early evening Mumbai is the only viable window.

USA (New York) ↔ Australia (Sydney)

Sydney is 14–16 hours ahead depending on DST

Best window: No true business-hours overlap. Best option: 8 AM Sydney / 5–6 PM NY previous day.

One side will always be outside standard hours. Mornings in Sydney work best.

United Kingdom (London) ↔ Singapore

Singapore is 8 hours ahead (no DST)

Best window: 9 AM–10 AM London / 5–6 PM Singapore

Very narrow. End of Singapore business day aligns with start of London day.

USA (Los Angeles) ↔ United Kingdom (London)

London is 8 hours ahead in winter, 7 hours in summer

Best window: No clean overlap in winter. Summer: 9 AM–10 AM LA / 4–5 PM London.

LA–London is one of the hardest pairs. Afternoon London calls work best.

USA (New York) ↔ Germany (Berlin)

Berlin is 6 hours ahead in winter, 5 hours in summer

Best window: 9 AM–12 PM New York / 3–6 PM Berlin

Solid three-hour overlap in the morning NY / afternoon Berlin window.

Australia (Sydney) ↔ United Kingdom (London)

Sydney is 10–11 hours ahead

Best window: 8–9 AM London / 6–7 PM Sydney

Start of London day / end of Sydney day. Both sides are stretching their hours.

Watch out for DST transition weeks

The windows above shift by one hour during DST transitions — and the US and EU switch on different dates, creating a two to three week period where the gap between them is one hour different from usual. If you have a recurring call, double-check the time in the weeks around:

Second Sunday of March (US springs forward)
Last Sunday of March (EU springs forward)
Last Sunday of October (EU falls back)
First Sunday of November (US falls back)

Tools to find the right time instantly

Rather than doing the math manually, use the timezone converter to enter a proposed time and see what it means for any city instantly. Or use the world clock to see current times side by side for multiple cities.