JSFiddle - React, Tailwind, and code Playground

HTML

<div class='button'>ABI
    <div>12/19</div>
</div>

CSS

* {
    margin:0;
    padding:0;
    box-sizing:border-box;
}
.button, .button div {
    color:grey;
    background:#007bff;
    display:inline-block;
    line-height:60px;
    font-size:20px;
}
.button div {
    padding-right:25px;
    padding-left:25px;
    width:180px;
    -webkit-border-top-right-radius: 5px;
    -webkit-border-bottom-right-radius: 5px;
    -moz-border-radius-topright: 5px;
    -moz-border-radius-bottomright: 5px;
    border-top-right-radius: 5px;
    border-bottom-right-radius: 5px;
    z-index:1;
    text-align:left;
    position:relative;
}
.button {
    color:#007bff;
    background:grey;
    padding-left:25px;
    width:280px;
    text-align:right;
    -webkit-border-radius: 5px;
    -moz-border-radius: 5px;
    border-radius: 5px;
    position:relative;
    z-index:1;
}
.button div:after {
    content:'';
    display:block;
    position:absolute;
    left:0px;
    top:20px;
    width: 0px;
    height: 0px;
    border-style: solid;
    border-width: 10px 0 10px 14px;
    border-color: transparent transparent transparent grey;
    z-index:0;
}