var start = new Date();
start.setUTCHours(0,0,0,0);
var end = new Date();
end.setUTCHours(23,59,59,999);
alert( start.toUTCString() + ':' + end.toUTCString() );
var startOfDay = dateFns.startOfDay;
var endOfDay = dateFns.endOfDay;
console.log('start of day ==> ', startOfDay(new Date('2015-11-11')));
console.log('end of day ==> ', endOfDay(new Date('2015-11-11')));
// get current time for UTC timezone
const d = new Date();
const year = d.getUTCFullYear();
const month = d.getUTCMonth();
const day = d.getUTCDate();
// set time to begin day UTC
const startTime = Date.UTC(year, month, day, 0, 0, 0, 0);
//set time to end day UTC
const endTime = Date.UTC(year, month, day, 23, 59, 0, 0);