After a heavy meal during a lunch break (usually 60 minutes), one would return to there work desk.

Shortly after sitting down, tiredness would kick-in and prevent you from doing any work.

Thus entering Siesta Mode.

Times can vary, normally Siesta Mode peaks after 2pm.
Guy1 - That was a textbook lunch from the pub
Guy2 - Tell me about it!
Guy1 - Proper Siesta Mode now!
Guy2 - True, think I will lie down on my keyboard now.
by Avi-man December 9, 2009
Get the Siesta Mode mug.