Clockzilla is a free, precision world clock that synchronizes with NTP time servers to deliver millisecond-accurate time directly in your browser. Unlike your computer's built-in clock, which can drift over time, Clockzilla cross-references multiple atomic clock-referenced sources and applies statistical filtering for the most precise time possible.
Check the current time in any of 150,000+ cities across every timezone. See accurate local time, timezone abbreviation, UTC offset, sunrise and sunset times, and daylight saving time information.
Convert time between any two cities or timezones instantly. See the exact hour difference between locations, making it easy to schedule meetings, calls, and events across time zones.
View today's sunrise time, sunset time, and total daylight hours for your location or any city worldwide using the NOAA solar calculator algorithm.
Use the built-in stopwatch with lap tracking and split times, countdown timer with custom durations, or the Pomodoro productivity timer with automatic session cycling.
Browse a full calendar with US and international holidays, moon phases, and week numbers. Calculate days between dates or your exact age with the birthday calculator.
Clockzilla synchronizes with multiple time servers, measures round-trip latency, removes statistical outliers, and computes a weighted offset typically accurate within 50-500 milliseconds.
Clockzilla uses a multi-tier NTP-style synchronization engine. It sends requests to multiple time servers (TimeAPI.io and Cloudflare), measures round-trip network latency, removes statistical outliers using Median Absolute Deviation, and computes an RTT-weighted mean offset. The result tells you exactly how far ahead or behind your computer clock is.
Clockzilla synchronizes with NTP time servers to provide millisecond-accurate time. It measures network latency and statistically filters results for the most precise offset calculation.
Use the search bar to type any city name from the database of 150,000+ cities worldwide. The app instantly shows the accurate local time, timezone, sunrise, sunset, and DST information.
A timezone converter lets you compare the current time across different time zones simultaneously. It supports all IANA timezones and shows the offset between any two cities.
Yes, Clockzilla is completely free with no account required. It offers accurate time for 150,000+ cities, timezone conversion, sunrise/sunset times, a stopwatch, timer, Pomodoro timer, calendar, and more in 58 languages.