When you are dealing with lot of international clients, it becomes important to know whats their time and how many hours they are back or forth of you.  You might need is to you can send mails at right time or even call them at right time instead of first mailing to ask and call. You can avoid all these confusions with a simple trick which is available in your mail box.

I check with Gmail and Outlook and I am pretty sure its available with others.

Office Outlook :

• Right click on any mail
• Go to message options. The image below is what you should see where you would get details of PDT which is Pacific Day Time.

In Gmail :

• Open any email
• Then look for an option See Original mail
• It opens in new window and you can see al mail headers etc

Basically every mail which is sent contains this information as part of Internet headers. containing server information, ip etc. In fact if you would like to know which computer the mail is sent from you can do that.