It's morning, evening, noon, midnight, dusk and dawn all at the same — this very — moment somewhere on earth.

Fortunately, any time is a good time to email. Unfortunately, not all times are fit to take phone calls. Before you call in response to an email, it's a courteous idea to check the time at the recipient's end.

How, you ask? It it difficult, but often, it can be done looking at their email's headers, then calculating to and fro a bit.

In Gmail, it can be done easily, if it can be done at all. All the calculations behind the scenes and under its belt, Gmail will even break down the sender's current local time to a phonographic traffic lights: green means call (9-6), red means mail (6-9).

If you're curious (and who would not be?), you can also find out what local time an email was sent just for fun, and what the time is right now for the sender.

See the Sender's Local Time in Gmail

Note that sender time zone icons are currently not available in Gmail.

To have Gmail calculate and show other people's local time:

• Click the Settings gear in Gmail's toolbar.
• Select Settings from the menu.
• Go to the Labs tab.
• Make sure Enable is selected for Sender Time Zone.
• Click Save Changes.

To see when a message was sent in the sender's local time and what time it is for them now:

• Open a message.
• Click show details.
• Under sender-time, find both when the email was sent, and what the local time is now at the sender's end.
• In additional, a phone icon tells you whether the sender is likely to be accessible right now:
  • green: between 9 am and 6 pm sender local time
  • red: between 6 pm and 9 am sender local time.

(Updated November 2012)