use <neon-animatable> instead of <section is="neon-animatable">
use <neon-animatable> instead of <section is="neon-animatable">

mhuon/paper-date-picker,Custom-Elements/paper-date-picker,Mipme/paper-date-picker,bendavis78/paper-date-picker,Mipme/paper-date-picker,Custom-Elements/paper-date-picker