IANA Time Zone Database

The standardized time zone system used by computers worldwide

What is IANA?

The IANA Time Zone Database (also called tzdata or zoneinfo) is the gold standard for time zone information. Maintained by the Internet Assigned Numbers Authority (IANA), it contains:

All recognized time zone names
UTC offsets for every zone
Historical time changes going back decades
Daylight saving rules
Time zone abbreviations

Every major operating system and programming language uses this database.

IANA Time Zone Format

IANA time zones use the format Region/City:

America/New_York
Europe/London
Asia/Tokyo
Australia/Sydney
Pacific/Honolulu

Common IANA Time Zones

America/New_York - Eastern Time (ET)
America/Los_Angeles - Pacific Time (PT)
America/Chicago - Central Time (CT)
America/Denver - Mountain Time (MT)
Europe/London - GMT/BST (UK)
Europe/Paris - CET/CEST (France)
Europe/Berlin - CET/CEST (Germany)
Asia/Tokyo - Japan Standard Time
Asia/Shanghai - China Standard Time
Asia/Singapore - Singapore Time
Australia/Sydney - Australian Eastern Time
Pacific/Auckland - New Zealand Time

Why Use IANA?

Using IANA time zones provides:

Accuracy - Official, maintained data
Consistency - Same across all systems
Historical data - Account for past changes
Future-proof - Updated for DST changes

Programming Example

// JavaScript
const now = new Date();
console.log(now.toLocaleTimeString('en-US', {
  timeZone: 'America/New_York'
}));

// Python
from datetime import datetime
import pytz
tz = pytz.timezone('America/New_York')
print(datetime.now(tz))