{timestamp: 1521777600000, date: 'Thu, 23 Mar 2018 04:00:00 GMT'},
{timestamp: 1521950400000, date: 'Thu, 25 Mar 2018 04:00:00 GMT'},
{timestamp: 1522296000000, date: 'Thu, 29 Mar 2018 04:00:00 GMT'}
];
let ticksPerDay = getTicks(timestamps, 'timestamp');
// expect 1 tick (timestamp) for each day between March 22 - March 29
{timestamp: 1521777600000, date: 'Thu, 23 Mar 2018 04:00:00 GMT'},
{timestamp: 1521950400000, date: 'Thu, 25 Mar 2018 04:00:00 GMT'},
{timestamp: 1522296000000, date: 'Thu, 29 Mar 2018 04:00:00 GMT'}
];
let ticksPerDay = getTicks(timestamps, 'timestamp');
// expect 1 tick (timestamp) for each day between March 22 - March 29