If you are using Bootstrap 3 Datepicker and want to change the icons used for the symbols within the datepicker then you can.

On initialisation you can add an icons property and specify each icon you want.

You probably knew this because like a good developer you read the documentation.

What the documentation doesn’t tell you is the names you need to use for them all.

Through trial and error (and looking at the source code) I was able to grab them all.

    icons: {
      time: "fa fa-clock-o",
      date: "fa fa-calendar",
      up: "fa fa-caret-up",
      down: "fa fa-caret-down",
      previous: "fa fa-caret-left",
      next: "fa fa-caret-right",
      today: "fa fa-today",
      clear: "fa fa-clear",
      close: "fa fa-close"

I hope this saves someone the 30 minute search I had to go on!