Every December the same message appears in family chats: "Shall we all video call on Christmas Day? Say 2pm?" Two pm where? For Gran in London it is mid-afternoon. For a cousin in Toronto it is breakfast. For a sister in Auckland it is three in the morning on Boxing Day.
Picking a call time across time zones is not hard, but it is easy to get wrong by guessing. This guide gives you a method you can do on paper in about ten minutes, then walks through a full worked example with four cities on Christmas Day 2026. At the end there is a quicker way to do the same sums.
Why holiday calls go wrong
Most scheduling mistakes come from four habits:
- Quoting your own time. "2pm" only means something to the person who said it.
- Forgetting the date line. When it is Friday evening in London it is already Saturday morning in Auckland. A call on "Christmas Day" can fall on two different days for two different people.
- Assuming everyone shares the same summer time. In December, Sydney, Melbourne and Auckland are on summer time. London and Toronto are on winter time. Johannesburg, Perth and Brisbane do not change at all.
- Ignoring the ordinary day. A call that lands in the middle of a Christmas dinner, or at 5am, is technically possible and practically useless.
The fix is to do two things before suggesting a time: convert everyone to one shared clock, and write down each person's comfortable hours first.
The method in five steps
- Fix the date and the call length. Decide which calendar day you mean, and how long you want to talk. Fifteen minutes is a catch-up. Thirty is a proper chat. Sixty is a full family call with the kids passed around.
- Write each person's comfortable window. This is the earliest and latest local time they would happily join. Eight in the morning to ten at night is a sensible default. Night owls and early risers can stretch it. If someone's window crosses midnight, such as 20:00 to 02:00, write it that way.
- Add any do not call time. Christmas lunch, a church service, a nap for a toddler. Write it down as a local-time block.
- Convert every window to one shared clock. UTC is the easiest, because it has no summer time of its own. Subtract the person's offset from their local time to get UTC.
- Find where all the windows overlap, then fit the call inside. The overlap has to be at least as long as the call. If it is not, you are choosing between a shorter call and someone stretching their day.
That is the whole method. The only tricky part is step four, because offsets depend on the exact date.
Get the offsets right for the date
A time zone offset is how far a place is ahead of or behind UTC. It changes when a place moves its clocks, so always look it up for the date you are actually using. For 25 December 2026, these are the offsets for some places families often live in:
| Place | Offset from UTC on 25 Dec | Note |
|---|---|---|
| London | +0:00 | Winter time |
| Toronto and Chicago | -5:00 and -6:00 | Winter time |
| Johannesburg | +2:00 | No clock change |
| Mumbai and Delhi | +5:30 | Half-hour offset |
| Kathmandu | +5:45 | Forty-five minute offset |
| Perth | +8:00 | No clock change |
| Adelaide | +10:30 | Summer time, half-hour offset |
| Sydney and Melbourne | +11:00 | Summer time |
| Auckland | +13:00 | Summer time |
Two things stand out. The southern hemisphere is on summer time while the north is on winter time, so the gap between London and Sydney is eleven hours in December but nine hours in July. And a few places, such as Mumbai, Adelaide and Kathmandu, sit on a half-hour or forty-five-minute offset, so mental arithmetic on whole hours quietly goes wrong.
A worked example: four cities on Christmas Day
Here is a realistic family. Christmas Day 2026 falls on a Friday. We want a thirty-minute call, and everyone is happy to join between 08:00 and 22:00 their own time.
- Gran in London
- A cousin in Toronto
- An uncle in Johannesburg
- A sister in Auckland
Step 1: convert each window to UTC
Subtract each offset from the local times. For Auckland, remember that its Christmas Day starts long before London's, so its comfortable hours on the 25th are largely over by the time London wakes up. The Auckland time we care about is the morning of Saturday 26 December, which is still Friday evening in London.
| Person | Local window | Offset | Window in UTC |
|---|---|---|---|
| London | 08:00 to 22:00 | +0:00 | 08:00 to 22:00 |
| Toronto | 08:00 to 22:00 | -5:00 | 13:00 to 03:00 next day |
| Johannesburg | 08:00 to 22:00 | +2:00 | 06:00 to 20:00 |
| Auckland, Sat 26 Dec | 08:00 to 22:00 | +13:00 | 19:00 Fri to 09:00 Sat |
Step 2: find the overlap
Take the latest start and the earliest end across all four windows. The latest start is Auckland's 19:00 UTC. The earliest end is Johannesburg's 20:00 UTC. The overlap is therefore 19:00 to 20:00 UTC, which is one hour.
Convert that hour back to each person's own clock:
| Person | Overlap in local time | Day |
|---|---|---|
| London | 19:00 to 20:00 | Friday 25 Dec |
| Toronto | 14:00 to 15:00 | Friday 25 Dec |
| Johannesburg | 21:00 to 22:00 | Friday 25 Dec |
| Auckland | 08:00 to 09:00 | Saturday 26 Dec |
This is a tight fit. Johannesburg is nearly at bedtime, Auckland has barely had breakfast, and Toronto is just after lunch. But it works, and the date difference is clear: the Christmas Day call is Boxing Day morning for Auckland.
Step 3: fit the call inside
A thirty-minute call can start anywhere from 19:00 to 19:30 UTC. A forty-five minute call can start from 19:00 to 19:15. A sixty-minute call fits only if it starts at exactly 19:00 UTC, with no slack for anyone.
The best choice is usually the start with the most room at the tightest edge. Here that is 19:15 UTC: it leaves fifteen minutes before Auckland's earliest time and fifteen minutes before Johannesburg's latest. In local terms:
- London: 19:15 on Friday 25 December
- Toronto: 14:15 on Friday 25 December
- Johannesburg: 21:15 on Friday 25 December
- Auckland: 08:15 on Saturday 26 December
Step 4: add the do not call time
Now suppose the Toronto family eats Christmas dinner from 14:30 to 16:30. Everyone else's local clock is nowhere near that window at the call time, but Toronto's matters: a call at 14:15 would run until 14:45 and collide with dinner.
With that block in place, a thirty-minute call has only one start left, 19:00 UTC, which is 14:00 in Toronto and finishes exactly as dinner begins. There is no spare time, so you would say so in the invite and ask Toronto to be ready at 14:00 sharp. That is the value of writing the block down before you propose a time.
Step 5: what if there is no overlap?
Change the example so that Auckland's earliest time is 09:00 instead of 08:00. Auckland's window now opens at 20:00 UTC, the very minute Johannesburg's closes, so the overlap is zero. When that happens, do not guess. Look for the nearest near-miss: the start where the person who has to stretch the most stretches the least. Here the best try is 19:45 in London, 14:45 in Toronto, 21:45 in Johannesburg and 08:45 on Saturday in Auckland. Johannesburg and Auckland each join fifteen minutes outside their window, and London and Toronto are comfortable. For a once-a-year call that is usually an easy ask.
Showing the miss in minutes matters. "Could you join at 08:15 instead of 08:30?" is a reasonable request. "Nothing works" ends the conversation.
Choosing between several workable times
When more than one start time fits, rank them. Three simple rules help:
- Spare room first. Prefer the time that is furthest from anyone's limit, so a late start or a short overrun does not push someone out of their window.
- Middle of the day beats the edges. A call in the middle of each person's day is more relaxed than one at the very start or end.
- Keep alternatives apart. Offer options at least half an hour apart. Two choices ten minutes apart are really one choice.
Then send one clear message with each person's local time and day, not a UTC time that someone has to convert themselves.
Write an invite everyone can read
A good invite names the occasion, gives the length, and lists every person's local time and day. For the example above:
Christmas Day call: 30 minutes
- Gran (London): Fri 25 Dec, 19:15
- Cousin (Toronto): Fri 25 Dec, 14:15
- Uncle (Johannesburg): Fri 25 Dec, 21:15
- Sister (Auckland): Sat 26 Dec, 08:15 (next day)
Reply with a thumbs up, or suggest another time.
Notice the "(next day)" note. It prevents the single most common misunderstanding on a holiday call, which is someone turning up a day early or a day late.
Special cases worth knowing
Windows that cross midnight. A night owl might say "any time from 20:00 to 02:00". Treat it as one continuous window from 20:00 to 26:00 on a 24-hour clock. When you compare it with others, the early-morning half belongs to the next calendar day.
Half-hour and forty-five minute places. Convert in minutes, not hours. A call at 19:15 UTC is 00:45 the next day in Mumbai and 01:00 in Kathmandu. Anyone calling Nepal from London should work out the forty-five minutes carefully.
Two people in the same zone. If two relatives share a time zone, they share a clock. List both anyway if they have different comfortable hours, because the stricter window wins.
31 December and 1 January. The same date-line problem is bigger here. Auckland reaches midnight first, thirteen hours before London, while Honolulu is among the last big cities to celebrate. A video call that spans the countdown is only possible for people within a few hours of each other, so many families plan a short call early in the evening for everyone and a second one later for those in the same region.
Do it in a minute instead
The method above is reliable, but converting four windows by hand is slow, and a half-hour offset or a southern summer time is easy to miss. The Holiday call time finder does the same steps for you. Pick a date from 24 to 26 December or 31 December to 1 January, choose two to six places, set each person's earliest and latest time, add an optional do not call window and the call length. It returns ranked start times with everyone's own clock and day, a 24-hour strip for each person, an invite message you can copy, a printable sheet for A4 or US Letter and a CSV.
It works out every offset from the exact date you choose, so summer time is handled, and nothing you type leaves your device.
If you are counting down to the day itself, the holiday countdown card maker makes a shareable days-to-go card for the family chat, and the holiday planning calendar guide helps you fit the rest of the season around the call.
Frequently asked questions
What is the best time for a call across many time zones?
The best time is the start with the most spare room at the tightest edge, inside everyone's comfortable hours and clear of meals. List each person's earliest and latest local time, convert to one shared clock, find the overlap, and choose the middle of it.
How do I handle daylight saving time?
Look up each place's offset for the exact date of the call. In December, Sydney, Melbourne and Auckland are on summer time, London and Toronto are on winter time, and Johannesburg, Perth and Brisbane do not change. Never reuse an offset from another time of year.
Which day is the call on if one person is already in the next day?
The call has one moment but can have two calendar days. When you invite people, write each person's local day next to their time, with a "next day" or "day before" note, so nobody misses it.
What if no time works for everyone?
Find the nearest near-miss and say by how many minutes each person would stretch. A fifteen-minute stretch for one person is usually fine for a holiday call. If it is more, shorten the call or hold two shorter calls.