Timing of Backswing, Downswing and Backswing/Downswing Ratio
Putting stroke tempo is calculated as the ratio of backswing / downswing. The slower the backswing compared to downswing the higher the ratio. The quicker the downswing, the higher the tempo. Swing tempo is very important for putting consistency.
The best putters in the world have very consistent timing regardless of the length of the putt. Improving the tempo improves distance control and consistency.
Usually the best putters have a ratio close to 2.0. The putting backstroke time is around 0.6 seconds and downstroke time is around 0.3 seconds.
The top of the backswing is identified when the hand movement is changing direction.