If your girl friend was born at 3:00AM and you would like to wish her exactly at 3:00AM rather than wishing at 12:AM when she is in other side of the globe, what can you do? Because there are 12 hours of time difference between both of you. Don’t panic, here is the perfect solution for you from Gmail. You can enable this Sender Time Zone feature from Labs tab under settings, and then you will have green phone icons next to people who are probably awake.
In addition, the red icons next to those represent who could be sleeping or out of the office. The time zone to get your friend is between 9:00 am and 6:00 pm according to your friend’s local time zone.