How to get scale of specific date on x-axis, D3?

[Shoosha]

I created a D3 graph and colored it by x-axis scale:

coloring graph by scale

My grpah color

My x-axis tick info is, eg: Thu Jan 01 2004 00:00:00 GMT+0200 (Canada)

I want to color it by date. eg: between 1/1/2014- 1/5/2016 color it blue. What is the best way to get the x-axes scale (0-1) of a specific date?

THANK YOU!