Hi,
Put both date values in two variables in JS function.
Then Use
var googleURL = "https://www.googleapis.com/analytics/v3/data/ga?ids=ga%3A76546294&dimensions='ga%3Asource&metrics=ga%3Ausers&sort=-ga%3Ausers&start-date='"+Date1+"'&end-date='"+Date2+"'&max-results=10;'"
Pls check by using this, then tell me it is solved or not.