From: Ashar Malik (asharjm_at_gmail.com)
Date: Wed May 27 2015 - 21:54:20 CDT

   1.

   Select *Extensions:Analysis:Timeline* from "VMD Main" window.
   2.

    display a 2D graph of secondary structure vs. time, select
   Calculate:Calc Sec. Struct. from the "VMD Timeline" window. A color-coded
   map of secondary structure should appear. The horizontal axis is time
   (frame number), the vertical axis is residue number/chain.

Source: http://www.ks.uiuc.edu/Research/vmd/plugins/timeline/