CodePen Embed - Calendar

<div class="calendar">
  <div class="calendar__opts">
    <select name="calendar__month" id="calendar__month">
      <option>Jan</option>
      <option>Feb</option>
      <option>Mar</option>
      <option>Apr</option>
      <option selected>May</option>
      <option>Jun</option>
      <option>Jul</option>
      <option>Aug</option>
      <option>Sep</option>
      <option>Oct</option>
      <option>Nov</option>
      <option>Dec</option>
    </select>

    <select name="calendar__year" id="calendar__year">
      <option>2017</option>
      <option>2018</option>
      <option>2019</option>
      <option selected>2020</option>
    </select>
  </div>

  <div class="calendar__body">
    <div class="calendar__days">
      <div>M</div>
      <div>T</div>
      <div>W</div>
      <div>T</div>
      <div>F</div>
      <div>S</div>
      <div>S</div>
    </div>

    <div class="calendar__dates">
      <div class="calendar__date calendar__date--grey"><span>27</span></div>
      <div class="calendar__date calendar__date--grey"><span>28</span></div>
      <div class="calendar__date calendar__date--grey"><span>29</span></div>
      <div class="calendar__date calendar__date--grey"><span>30</span></div>
      <div class="calendar__date"><span>1</span></div>
      <div class="calendar__date"><span>2</span></div>
      <div class="calendar__date"><span>3</span></div>
      <div class="calendar__date"><span>4</span></div>
      <div class="calendar__date"><span>5</span></div>
      <div class="calendar__date"><span>6</span></div>
      <div class="calendar__date"><span>7</span></div>
      <div class="calendar__date"><span>8</span></div>
      <div class="calendar__date"><span>9</span></div>
      <div class="calendar__date"><span>10</span></div>
      <div class="calendar__date"><span>11</span></div>
      <div class="calendar__date"><span>12</span></div>
      <div class="calendar__date"><span>13</span></div>
      <div class="calendar__date"><span>14</span></div>
      <div class="calendar__date"><span>15</span></div>
      <div class="calendar__date calendar__date--selected calendar__date--first-date calendar__date--range-start"><span>16</span></div>
      <div class="calendar__date calendar__date--selected calendar__date--last-date"><span>17</span></div>
      <div class="calendar__date calendar__date--selected calendar__date--first-date"><span>18</span></div>
      <div class="calendar__date calendar__date--selected"><span>19</span></div>
      <div class="calendar__date calendar__date--selected"><span>20</span></div>
      <div class="calendar__date calendar__date--selected calendar__date--last-date calendar__date--range-end"><span>21</span></div>
      <div class="calendar__date"><span>22</span></div>
      <div class="calendar__date"><span>23</span></div>
      <div class="calendar__date"><span>24</span></div>
      <div class="calendar__date"><span>25</span></div>
      <div class="calendar__date"><span>26</span></div>
      <div class="calendar__date"><span>27</span></div>
      <div class="calendar__date"><span>28</span></div>
      <div class="calendar__date"><span>29</span></div>
      <div class="calendar__date"><span>30</span></div>
      <div class="calendar__date"><span>31</span></div>
    </div>
  </div>

  <div class="calendar__buttons">
    <button class="calendar__button calendar__button--grey">Back</button>

    <button class="calendar__button calendar__button--primary">Apply</button>
  </div>
</div>

.calendar {
  --side-padding: 20px; // padding to be applied to the side of the calendar
  --border-radius: 34px; // border-radius of the main calendar shell
  --accent-br: 15px; // border-radius for accents under dates on hover

  width: 400px;

  select {
    background-color: #f3f4f6;
    padding: 15px 20px;
  }

  &__opts,
  &__buttons {
    background-color: #fff;
    display: grid;
    grid-template-columns: 1fr 1fr;
    column-gap: 15px;
  }

  &__opts {
    border-top-left-radius: var(--border-radius);
    border-top-right-radius: var(--border-radius);
    padding: 20px var(--side-padding);
  }

  &__body {
    background-image: linear-gradient(to bottom, #f3f4f6, #fff);
  }

  &__days {
    background-color: #fff;
    padding: 0 var(--side-padding) 10px;
    display: grid;
    grid-template-columns: repeat(7, 1fr);

    & > div {
      text-align: center;
      font: {
        weight: 700;
        size: 1.02rem;
      }
      color: #c5c8ca;
    }
  }

  &__dates {
    padding: 10px var(--side-padding);
    display: grid;
    grid-template-columns: repeat(7, 1fr);
  }

  &__date {
    --height: calc(400px / 6 - var(--side-padding));

    text-align: center;
    height: var(--height);
    line-height: var(--height);
    font: {
      weight: 600;
      size: 1.02rem;
    }
    cursor: pointer;
    position: relative;

    &::before {
      content: "";
      position: absolute;
      background-color: rgba(255, 255, 255, 0);
      width: 100%;
      height: calc(var(--height) * 0.9);
      top: 50%;
      left: 50%;
      transform: translate(-50%, -50%);
      border-radius: var(--accent-br);
      transition: background-color 0.3s ease;
    }

    &:not(.calendar__date--selected):not(.calendar__date--grey):hover::before {
      background-color: #ededed;
    }

    &--grey {
      color: #c5c8ca;
      cursor: not-allowed;
    }

    &--selected {
      color: #ff374b;

      &::before {
        background-color: #ffeaec;
        border-radius: 0px;
      }
    }

    &--first-date {
      &::before {
        border-top-left-radius: var(--accent-br);
        border-bottom-left-radius: var(--accent-br);
      }
    }

    &--last-date {
      &::before {
        border-top-right-radius: var(--accent-br);
        border-bottom-right-radius: var(--accent-br);
      }
    }

    &--range-start {
      &::after {
        content: "";
        position: absolute;
        bottom: 3px;
        border-radius: 24px;
        left: 50%;
        transform: translateX(-50%);
        background-color: #ff374b;
        width: 10px;
        height: 4px;
      }
    }

    &--range-end {
      color: #fff;

      &::before {
        box-shadow: 0 15px 20px -3px rgba(255, 55, 75, 0.35);
        background-color: #ff374b;
        border-radius: var(--accent-br);
        z-index: 1;
      }

      &::after {
        content: "";
        position: absolute;
        height: calc(var(--height) * 0.9);
        background-color: #ffeaec;
        width: 50px;
        top: 50%;
        right: 50%;
        transform: translateY(-50%);
      }
    }

    span {
      position: relative;
      z-index: 1;
    }
  }

  &__buttons {
    padding: 10px var(--side-padding) 20px;
    border-bottom-left-radius: var(--border-radius);
    border-bottom-right-radius: var(--border-radius);
  }

  &__button {
    cursor: pointer;

    &--grey {
      background-color: #f3f4f6;
    }

    &--primary {
      background-color: #1752ff;
      color: #fff;
      transition: box-shadow 0.3s cubic-bezier(0.21, 0.68, 0.09, 0.27),
        transform 0.2s linear;

      &:hover {
        box-shadow: 0 20px 30px -13px rgba(23, 82, 255, 0.45);
        transform: translateY(-3px);
      }

      &:active {
        box-shadow: 0 10px 10px -6px rgba(23, 82, 255, 0.45);
        transform: translateY(-1px);
      }
    }
  }
}

body {
  display: grid;
  place-items: center;
  background-color: #eaedf2;
  height: 100vh;
  font: {
    family: "Nunito", sans-serif;
    size: 14px;
  }
  margin: 3vmin;
}

select,
button {
  font: {
    family: inherit;
    weight: 700;
    size: 1.02rem;
  }
  border-radius: 20px;
  outline: none;
  border: 0;
  padding: 15px 20px;
  -webkit-appearance: none;
  -moz-appearance: none;
  appearance: none;
}

select {
  background: {
    image: url("data:image/svg+xml,%3C%3Fxml version='1.0' encoding='utf-8'%3F%3E%3C!DOCTYPE svg PUBLIC '-//W3C//DTD SVG 1.1//EN' 'http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd'%3E%3Csvg version='1.1' id='Capa_1' xmlns='http://www.w3.org/2000/svg' xmlns:xlink='http://www.w3.org/1999/xlink' x='0px' y='0px' width='960px' height='560px' viewBox='0 0 960 560' enable-background='new 0 0 960 560' xml:space='preserve'%3E%3Cg id='Rounded_Rectangle_33_copy_4_1_'%3E%3Cpath d='M480,344.181L268.869,131.889c-15.756-15.859-41.3-15.859-57.054,0c-15.754,15.857-15.754,41.57,0,57.431l237.632,238.937 c8.395,8.451,19.562,12.254,30.553,11.698c10.993,0.556,22.159-3.247,30.555-11.698l237.631-238.937 c15.756-15.86,15.756-41.571,0-57.431s-41.299-15.859-57.051,0L480,344.181z'/%3E%3C/g%3E%3C/svg%3E");
    size: 24px;
    repeat: no-repeat;
    position: calc(100% - var(--side-padding)) center;
  }
}

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This Pen is owned by Mark Eriksson on CodePen.

See more by @Markshall on CodePen

External CSS

https://fonts.googleapis.com/css2?family=Nunito:ital,wght@0,400;0,700;1,600&display=swap

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