World Clock, Time Zone Converter & Countdown
See real-time clocks for cities worldwide, convert time zones, plan meetings, run timers and stopwatches, and share countdowns to the events that matter - all free.
Essential tools
World Clock
Check current time in cities around the world
Time Converter
Easily convert time between two cities
Countdown
Time remaining until holidays and events worldwide
More tools
Timer
Free online timer with alarm sound. Set any duration and start with one click.
Clock
A beautiful fullscreen clock for classrooms, cafes, gyms, and streamers
Today
Today's holidays and historical events
Awake
Real-time estimate of how many people are awake on Earth
Population
Real-time world population estimate based on UN data. View births, deaths, and regional statistics.
Date Calc
Calculate your exact age from your date of birth
Year Progress
Visualize how much of the year has passed in real time
Articles
In-depth articles about time and timezones
Glossary
Key terms about time and timezones explained
Popular Articles
Will Leap Seconds Be Abolished? - The International Agreement Toward 2035 and Its Technical Impact
In 2022, the General Conference on Weights and Measures (CGPM) adopted Resolution 4 to increase the maximum allowed difference between UT1 and UTC in or before 2035, which in practice brings the insertion of leap seconds to an end; as of September 2026, the new limit and its start date have not yet been decided. This article covers the gap between atomic time and astronomical time, why leap seconds break IT systems, and how leap smearing has buffered the issue in the meantime.
TechnologyDistributed Databases and Time - Causal Order and Logical Clocks
Distributed systems cannot agree on a single global clock, which makes ordering events surprisingly hard. This article covers the impossibility of perfect global time, Lamport and vector clocks, Google Spanner's TrueTime, and the Hybrid Logical Clock that powers CockroachDB.
TechnologyUTC Conversion in Programming - The Right Patterns for Time Zones
The cardinal rule of timestamp handling in software is store in UTC, display in local. This article covers the rationale, ISO 8601 formatting, JavaScript patterns, the most common bugs, and a testing strategy that catches DST and date-line issues before they reach production.
TechnologyTime Display Formats - Designing for 12-Hour, 24-Hour, and Locales
Choosing how to display time looks simple but involves locale conventions, the AM/PM ambiguity at midnight and noon, ISO 8601 versus human-friendly forms, and relative time strings. This article guides UI designers and developers through the design decisions that matter most.
TechnologyHow Stopwatches Work - From Mechanical Movements to GPS Timing
A stopwatch measures elapsed time, not absolute time, and that distinction shapes its design. From mechanical pocket watches to quartz, electronic photo-finish, and GPS-synchronized track-side systems, stopwatch technology has evolved to meet ever-tighter precision demands.
TechnologyHow TOTP Works - The 6-Digit Code Behind Google Authenticator
The 6-digit codes shown by Google Authenticator and similar apps are generated from a shared secret and the current time. This article explains the TOTP algorithm defined in RFC 6238, the difference from HOTP, common time-drift failure modes, and what is actually inside the QR code you scan during setup.