datepicker.css

.datepicker {
  color: black;
  position: absolute;
  width: 250px;
  display: -ms-flexbox;
  display: flex;
  -ms-flex-direction: column;
      flex-direction: column;
  font-family: sans-serif;
  font-size: 14px;
  z-index: 9001;
  -webkit-user-select: none;
     -moz-user-select: none;
      -ms-user-select: none;
          user-select: none;
  border: 1px solid gray;
  border-radius: 4.22275px;
  overflow: hidden;
  background: white;
  box-shadow: 0 20px 20px -15px rgba(0, 0, 0, 0.3);
}
.datepicker * {
  box-sizing: border-box;
}
.datepicker.hidden {
  display: none;
}
.controls {
  width: 100%;
  display: -ms-flexbox;
  display: flex;
  -ms-flex-pack: justify;
      justify-content: space-between;
  -ms-flex-align: center;
      align-items: center;
  -ms-flex-positive: 1;
      flex-grow: 1;
  -ms-flex-negative: 0;
      flex-shrink: 0;
  background: lightgray;
}
.arrow {
  height: 25px;
  width: 25px;
  position: relative;
  cursor: pointer;
}
.arrow:hover.left:after {
  border-right-color: black;
}
.arrow:hover.right:after {
  border-left-color: black;
}
.arrow:after {
  content: '';
  border: 6.25px solid transparent;
  position: absolute;
  top: 50%;
  transition: border .2s;
}
.arrow.left:after {
  border-right-color: gray;
  right: 50%;
  transform: translate(25%, -50%);
}
.arrow.right:after {
  border-left-color: gray;
  left: 50%;
  transform: translate(-25%, -50%);
}
.month-year {
  font-weight: bold;
}
.month {
  padding-right: .5ex;
}
.year {
  padding-left: .5ex;
}
.squares {
  display: -ms-flexbox;
  display: flex;
  -ms-flex-wrap: wrap;
      flex-wrap: wrap;
  padding: 5px;
}
.square {
  width: 14.28571429%;
  height: 25px;
  display: -ms-flexbox;
  display: flex;
  -ms-flex-align: center;
      align-items: center;
  -ms-flex-pack: center;
      justify-content: center;
  cursor: pointer;
  transition: background .1s;
  border-radius: 4.22275px;
}
.square.current {
  font-weight: bold;
}
.square.active {
  background: lightblue;
}
.square.disabled span {
  opacity: .2;
}
.square.empty {
  cursor: default;
}
.square.disabled {
  cursor: not-allowed;
}
.square.day {
  cursor: default;
  font-weight: bold;
  color: gray;
}
.square:not(.empty):not(.disabled):not(.day):hover {
  background: orange;
}