New in Gmail Labs: Sender time zone

Gmail has introduced a new feature in Gmail Labs called Sender Time Zone. You can turn it on from the Labs tab under Settings, and you'll see green phone icons next to people who are probably awake and readily reachable (if it's between 9:00 am and 6:00 pm in the sender's local time zone) and red ones next to those who could be sleeping or out of the office:

Click "show details" and you can see when a message was sent in the sender's time zone as well as what time it is for them now:

Message headers always include the time sent and often include time zone info too.

Read the complete post at Official Gmail Blog: New in Labs: Sender time zone