AM and PM: What Do They Mean? - timeanddate.com
Ante meridiem is commonly denoted as AM, am, a.m., or A.M.; post meridiem is usually abbreviated PM, pm, p.m., or P.M. Like many other sources, timeanddate.com uses “am” and …
UTC Time Standard - timeanddate.com
Aug 26, 2025 · UTC is a time zone standard used as a basis for all time zones worldwide. It is a constant time scale and does not change for Daylight Saving Time (DST).
Greenwich Mean Time – GMT Time Zone
Information about the time zone abbreviation GMT – Greenwich Mean Time - where it is observed and when it is observed
How Long Is a Day on Earth? - timeanddate.com
How Far Back Does the Data Go? Super-accurate atomic clocks were first developed in the 1950s and 1960s. So measurements of the Earth's rotation using atomic clocks only go back …
Pacific Daylight Time – PDT Time Zone
This can add a bit of confusion as the term Pacific Time does not differentiate between standard time and Daylight Saving Time, so Pacific Time switches between PDT and PST in areas that …
Eastern Daylight Time – EDT Time Zone
This can add a bit of confusion as the term Eastern Time does not differentiate between standard time and Daylight Saving Time, so Eastern Time switches between EST and EDT in areas that …
UTC: Coordinated Universal Time
While you’re free to state any time around the world using the 12-hour time format with “am” and “pm” labels, UTC always uses the 24-hour clock, also known as military time.
India Standard Time – IST Time Zone / India Time
Information about the time zone abbreviation IST – India Standard Time - where it is observed and when it is observed
Central European Time – CET Time Zone / European Central Time
Information about the time zone abbreviation CET – Central European Time - where it is observed and when it is observed
Alaska Daylight Time – AKDT Time Zone
Information about the time zone abbreviation AKDT – Alaska Daylight Time - where it is observed and when it is observed