The short answer: World Time Buddy is a free, cross-platform web slider for comparing zones and eyeballing overlap. Atlas is a native macOS menu-bar app that recommends the best time automatically and writes it to your calendar in one tap, with no account and no tracking. Choose World Time Buddy for the occasional quick check on any device; choose Atlas if you schedule across zones regularly from a Mac.
These two tools get compared a lot, but they are really at different points in the same journey. World Time Buddy helps you see the time difference. Atlas helps you decide and book. Whether the difference matters depends on how often you do this.
What World Time Buddy does well
World Time Buddy is a browser-based tool with a clean hour-by-hour slider. You add cities, drag across the day, and read off everyone's local time. It overlays onto Google Calendar, lets you generate a shareable event page, and works on any operating system because it is just a web page. It is free (ad-supported, with a paid tier that removes ads), and for an occasional "what time is my call in Tokyo?" it is hard to beat.
If you only cross time zones now and then, or you are on Windows, Linux and Mac in the same week, a web tool that lives in a tab is a perfectly sensible choice.
Where Atlas goes further
Atlas is built for people who do this often and want it to feel native. It lives in the macOS menu bar, a keystroke away, and instead of asking you to read a slider, it shades each person's working hours and proposes the slot with the best overlap automatically. When you have a time, one tap writes the event to your calendar in everyone's correct local zone, daylight saving already handled. There is no account to create and no data leaves your Mac.
Side by side
| World Time Buddy | Atlas | |
|---|---|---|
| Platform | Web (any OS) | Native macOS app |
| Lives in | A browser tab | The menu bar, one keystroke away |
| Finds the overlap | You read it off the slider | Recommended automatically |
| Working-hours aware | Visual only | Shades each person's hours |
| Books the meeting | Manual / Google Calendar overlay | One tap to your calendar, in each local time |
| Account required | No (paid tier available) | No |
| Data collection | Ad-supported web app | None; nothing leaves your Mac |
| Price | Free, ads; paid tier | $9.99 once, no subscription |
Which should you choose?
Be honest about your usage. If you convert a time zone a couple of times a month, or you hop between operating systems, World Time Buddy is free and everywhere, and that convenience wins. There is no shame in a browser tab.
But if you coordinate meetings across zones most weeks, the small frictions add up: opening a tab, re-adding cities, eyeballing the overlap, then re-typing the event into your calendar and hoping you got the conversion right. Atlas collapses that into "open from the menu bar, pick the suggested time, tap to book." For a Mac-first workflow, that is the difference between a tool you visit and a tool that is just there.
Do you just need to know the time difference, or do you need to schedule a meeting? If it's the former, a free web slider is plenty. If it's the latter, and regularly, a native scheduler pays for itself fast.
The bottom line
World Time Buddy is an excellent free converter. Atlas is a native Mac scheduler that picks up where a converter stops, by recommending the time and writing it to your calendar. If you want to see how the overlap-finding and one-tap booking feel, take a look at what Atlas does, or read our method for scheduling a meeting across time zones.
Frequently asked
Is World Time Buddy free?
What does Atlas do that World Time Buddy doesn't?
Should I use a web tool or a native Mac app for time zones?
Stop doing timezone math
Atlas finds the time everyone's awake and adds it to your calendar in one tap.
One-time purchase, yours forever.