How to make use of it:

Include the stylesheet flatpickr.min.css and JavaScript flatpickr.min.js in your doc.

<link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/flatpickr/dist/flatpickr.min.css">
<script src="https://cdn.jsdelivr.net/npm/flatpickr"></script>

Attach a flat date picker to an input field.

<input id="flatpickr">

var example = flatpickr('#flatpickr');

Available choices with default values.

// flatpickr('selector', options);
flatpickr('#flatpickr',{

  // A string of characters which are used to define how the date will be displayed in the input box. 
  dateFormat: 'Y-m-d',

  // A reference to another input element. 
  // This can be useful if you want to show the user a readable date, but return something totally different to the server.
  altFormat: "F j, Y",

  // Exactly the same as date format, but for the altInput field
  altInput: false,

  // This class will be added to the input element created by the altInput option.  
  // Note that altInput already inherits classes from the original input.
  altInputClass: "",

  // Allows the user to enter a date directly input the input field. By default, direct entry is disabled.
  allowInput: false,

  // Instead of body, appends the calendar to the specified node instead.
  appendTo: null,
  
  // Defines how the date will be formatted in the aria-label for calendar days, using the same tokens as dateFormat. 
  // If you change this, you should choose a value that will make sense if a screen reader reads it out loud.
  ariaDateFormat: "F j, Y", 

  // Whether clicking on the input should open the picker. You could disable this if you wish to open the calendar manually with.open()
  clickOpens: true,

  // Sets the initial selected date(s).
  // If you're using mode: "multiple" or a range calendar supply an Array of Date objects or an Array of date strings which follow your dateFormat.
  // Otherwise, you can supply a single Date object or a date string.
  defaultDate: null,  
  
  // Initial value of the hour element.
  defaultHour: 12,  

  // Initial value of the minute element.  
  defaultMinute: 0, 

  // The minimum date that a user can start picking from, as a JavaScript Date.
  minDate: null,

  // The maximum date that a user can pick to, as a JavaScript Date. 
  maxDate: null,

  // Dates to disable, using intervals
  // disable: [ { 'from': '2015-09-02', 'to': '2015-10-02' } ]
  disable: null,

  // Set disableMobile to true to always use the non-native picker.
  // By default, flatpickr utilizes native datetime widgets unless certain options (e.g. disable) are used.
  disableMobile: false,
  
  // See Enabling dates
  enabl: [],

  // Enables time picker
  enableTime: false, 

  // Enables seconds in the time picker.
  enableSeconds: false, 

  // Allows using a custom date formatting function instead of the built-in handling for date formats using dateFormat, altFormat, etc.
  formatDate: null,  

  // Adjusts the step for the hour input (incl. scrolling)
  hourIncrement: 1, 

  // Displays the calendar inline
  inline: false,

  // Show the month using the shorthand version.
  shorthandCurrentMonth: false,

  // Adjusts the step for the minute input (incl. scrolling)
  minuteIncrement: 5,

  // "single"  "single", "multiple", or "range"
  mode: "single",

  // next/prev arrows
  prevArrow: '<',
  nextArrow: '>',

  // Function that expects a date string and must return a Date object
  parseDate: false,

  // Show the month using the shorthand version (ie, Sep instead of September).
  shorthandCurrentMonth: false,

  // Position the calendar inside the wrapper and next to the input element. (Leave false unless you know what you're doing.
  static: false,

  // Displays time picker in 24 hour mode without AM/PM selection when enabled. 
  time_24hr: false,

  // Enables display of week numbers in calendar.
  weekNumbers: false,

  // Hides the day selection in calendar.
  // Use it along with enableTime to create a time picker.
  noCalendar: false  
  
});

Callback features accessible.

flatpickr('#flatpickr',{

  // Function(s) to trigger on every date selection. 
  onChange: null  

  // Function(s) to trigger on every time the calendar is closed.
  onClose: null  

  // Function(s) to trigger on every time the calendar is opened.
  onOpen: null  

  // Function to trigger when the calendar is ready.
  onReady: null  
  
});

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