style.css

@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@400;500;600;700&display=swap');

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Poppins', sans-serif;
}

.flex{
    display: flex;
    align-items: center;
    justify-content: center;
}

.container{
    width: 100%;
    height: 100vh;
    background: rgb(32,32,32);
}

.calendar{
    width: 430px;
    height: 500px;
    background-color: white;
    box-shadow: 10px 10px 20px rgba(0,0,0,0.669), 
    -10px -10px 20px rgba(0,0,0,0.436);
}

.calendar .month{
    width: 100%;
    height: 20%;
    padding: 20px 30px;
    background-color: #ff9a8b;
    background-image: linear-gradient(90deg, #ff9a8b 0%, #ff6a88 55%, #ff99ac 100% );
    justify-content: space-between !important;
    text-align: center;
}

.calendar .month i{
    width: 26px;
    height: 26px;
    cursor: pointer;
    transition: 0.1s;
}

.month i:hover{
    opacity: 0.8;
}

.month h1{
    text-transform: uppercase;
    font-size: 30px;
}

.month p{
    font-weight: 300;
    color: rgba(0,0,0,0.797);
    font-family: cursive;
}

.weekdays{
    width: 100%;
    padding: 10px;
    height: 10%;
    padding-bottom: 0;
}

.weekdays div{
    width: calc(430px / 7);
    height: 80%;
    text-align: center;
    font-size: 16px;
    font-weight: 500;
    margin: 0 5px;
    transition: 0.2s;
}

.days{
    width: 100%;
    height: 70%;
    flex-wrap: wrap;
    margin: auto;
    padding: 30px 10px;
    padding-top: 0;
}

.days div{
    width: calc(400px / 7);
    height: calc(400px / 7);
    text-align: center;
    font-size: 13.5px;
    font-family: cursive;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: 0.1s;
}

.days .previous-days,
.days .next-days{
    color: rgba(0,0,0,0.349);
}

.days .today{
    background-color: #ff6a88;
    cursor: pointer;
    color: white;
    border-radius: 50%;
    transition: 0.2s;
}

.days .today:hover{
    background-color: #f95c79;
}

.days div:not(.today):hover{
    border-radius: 0;
    border: 0.5px solid black;
    background-color: rgba(0,0,0,0.215);
    cursor: pointer;
}