style.css

{
    outline:2px solid red;
}
html{
    height: 100%;
}
body{
    display: flex;
    justify-content: center;
    align-items: center;
    user-select: none;
    height: 675px;
    flex-direction: column;
    background: rgb(2,0,36);
    background: linear-gradient(45deg, rgba(2,0,36,1), rgba(0,212,255,1));
}
header{
    background-color: rgb(2,0,36,.1);
    width: 100vw;
    height: 58px;
    position: relative;
    top: -10px;
    margin-bottom: 1px;
    display: flex;
    justify-content: center;
    align-items: center;
    font-family: Arial;
    font-size: 22px;
    font-weight: bold;
}
.calendar{
    height: 80%;
    width: 590px;
    border-bottom: 1px solid rgb(255,255,255,.4);
    padding-bottom: 35px;
    border-radius: 5px;
}
.header{
    position: relative;
    display: flex;
    flex-direction: row;
    justify-content: space-evenly;
    align-items: center;
    font-family: "Century Schoolbook";
    width: 100%;
    height: 65px;
    border: 1px solid dimgray;
    background: linear-gradient(45deg, white, Floralwhite,white);
    opacity: .88;
    border-radius: 1vw;
}
.mainheader{
    display: flex;
    flex-direction: row;
    width: 100%;
    font-size: 15px;
    justify-content: center;
    margin-top: 15px;
    margin-bottom: 15px;
}
#prev, #next{
    border-radius: 8px;
    font-weight: bold;
    border: none;
    font-size: 20px;
    background-color: white;
    user-select: none;
}
#prev:hover, #next:hover{
    cursor: pointer;
    transform: scale(1.05);
}
#prev{
    position: relative;
    left: 15px;
    height: 30px;
}
#next{
    position: relative;
    right: 15px;
    height: 30px;
}
#changeYear{
    position: relative;
    right: -6%;
    display: flex;
    flex-direction: column;
    margin-right: 10px;
    display: none;
}
.header:hover #changeYear{
    display: flex;
}
.currentMonth{
    display: flex;
    justify-content: center;
}
#month-year{
    font-size: 20px;
}
.Dates{
    display: flex;
    flex-direction: column;
    justify-content: space-around;
    height: 90%;
}
.ROW1{
    display: flex;
    flex-direction: row;
    justify-content: space-evenly;
    color: darkred;
}
.ROW{
    display: flex;
    flex-direction: row;
    justify-content: space-evenly;
}
.COLUMN1{
    width: 30px;
    height: 25px;
    font-size: 22px;
    font-weight: bold;
    display: flex;
    justify-content: center;
    font-family: Calibri;
}
.COLUMN{
    width: 50px;
    height: 45px;
    border-radius: 20px;
    border: none;
    font-weight: bold;
    font-size: 18px;
    background-color: rgba(250, 250, 250, 0.5);
}
.COLUMN:hover{
    cursor: pointer;
    background-color: rgba(250, 250, 250, 0.5);

}
#month-year:hover, .ROW1:hover{
    cursor: default;
}
#todayTag{
    background-color: floralwhite;
    color: blue;
    font-family: Calibri;
    font-weight: bold;
    padding: 11px;
    border-radius: 15px;
    width: 5%;
    display: flex;
    justify-content: center;
    margin-right: 10%;
    opacity: .6;
}
#Date{
    background-color: floralwhite;
    color: blue;
    font-family: Calibri;
    font-weight: bold;
    padding: 11px;
    border-radius: 15px;
    opacity: .6;
}
.todayTag:hover{
    cursor: pointer;
    transition: 100ms;
    transform: scale(0.96);
}
@media(max-width: 1350px){
    .calendar{
        width: 600px;
    }
    .COLUMN{
        height: 46px;
        font-size: 18px;
    }
}
@media(max-width: 750px){
    header{
        position: absolute;
        top: 0px;
    }
    .mainheader{
        margin-top: 65px;
        margin-bottom: 8px;
    }
    .calendar{
        width: 420px;
    }
    .COLUMN{
        width: 46px;
        height: 40px;
        font-size: 17px;
        border-radius: 17px;
    }
    .COLUMN1{
        font-size: 21px;
    }
    #todayTag, #Date{
        display: flex;
        justify-content: center;
        font-size: 14px;
    }
    #todayTag{
        width: 8%
    }
}
@media(max-width: 450px){
    body{
        height: 635px;
    }
    .calendar{
        width: 350px;
        height: 430px;
        border-bottom: 1px solid rgb(255,255,255,.4);
    }
    .mainheader{
        margin-top: 40px;
        margin-bottom: 8px;
    }
    .header{
        border-radius: 2vw;
        background-color: floralwhite;
        display: flex;
        align-items: center;
    }
    #month-year{
        font-size: 18px;
    }
    .COLUMN{
        width: 38px;
        height: 36px;
        font-size: 13px;
        border-radius: 16px;
    }
    .COLUMN1{
        font-size: 14px;
    }
    #todayTag, #Date{
        display: flex;
        justify-content: center;
        font-size: 12px;
    }
    #todayTag{
        width: 10%
    }
}