new Date('2020-02-21' + 'T00:00');

// or

new Date('2020-02-21T00:00');

//or

const dateFromDateInput = '2020-02-21';
const dateFromTimeInput = '05:00';
cosnt baseDate = (new Date(`${dateFromDateInput}T${dateFromTimeInput}`));

//then, now you can use date-fns getUnixTime to turn it into timestamp
//turn timestamp into human readable date with fromUnixTime