An earthquake occurring anywhere in the world is marked with a timestamp. The UTC timestamp is the same no matter in which timezone you are located. An earthquake happening in Japan "right now" is also happening "right now" anywhere else. The only difference is . . . "right now" may be noon in Japan, but in Los Angeles, "noon" is 17 hours later. Similarly, while people in Japan may be tweeting about an earthquake that happened "5 minutes ago", Americans do not need to wait 17 hours to hear about it. It still happened "5 minutes ago" no matter where you are in the world.
The human readable date/time of an earthquake is reported in UTC - which is the more-widely used scientific replacement for GMT (Greenwich Mean Time). UTC is the time standard commonly used across the world. The world's timing centers have agreed to keep their time scales closely synchronized ( and coordinated ) hence the name
"Coordinated Universal Time".. Simply put, GMT is a time
zone, and UTC is a time
standard.
Examples:
Eastern Standard time in the U.S (i.e New York) is UTC - 5 hours.
UTC - 4h during daylight savings time.
Central time in the U.S (i.e Chicago) is UTC - 6 hours.
UTC - 5h during daylight savings time.
Coordinated Universal Time is 8 hours ahead of Pacific Time.
6:33 PM Thursday, Pacific Time (PT) = 2:33 AM Friday, Coordinated Universal Time (UTC)
To continually perform the math in your head can get confusing, so we convert the time of occurrence to local time for our members. We also convert the timestamp to
"friendly time ago". So, whatever the actual UTC timestamp may be,
"friendly time ago" tells you the earthquake happened
"this long ago" in readable English. Further calculation is then performed to convert that timestamp programmatically to your local time. The UTC timestamp is always the same for us, but your web browser knows what the local time is for you. We send the timestamp to the webpage you're looking at, and your browser will convert it. Additionally, when serving maps with latitude and longitude coordinates for earthquakes, the maps API can make a quick calculation relative to UTC, and display the local time of the occurrence.
