oms-Calendar/Theme/Backend/css/styles.scss

ul.btns {
    list-style: none;
    overflow: hidden;
    display: flex;

    li {
        background: var(--box-bg);;
        border-left: 1px solid var(--bborder);
        border-top: 1px solid var(--bborder);
        border-bottom: 1px solid var(--bborder);
        float: left;
        padding: 0 10px 0 10px;
        height: 2.5rem;
        position: relative;
        display: inline-flex;
        align-items: center;
        cursor: pointer;

        &:last-child {
            border-right: 1px solid var(--bborder);
        }

        &:before {
            border-left-color: var(--bborder);
            margin-left: 1px;
        }
    }

    .active, li:hover {
        background: var(--btn-bg);
        color: #fff;
    }
}

.m-calendar {
    width: 100%;

    ul {
        list-style: none;
        padding: 0;
        margin: 0;
        width: 100%;

        &.weekdays {
            height: 40px;

            li {
                text-align: center;
                text-transform: uppercase;
                line-height: 20px;
                border: none;
                color: #fff;
                padding: 10px 6px;
                font-size: 13px;
                background: var(--thead-bg);
            }
        }
    }

    li {
        display: block;
        float: left;
        width:14.285%;
        padding: 5px;
        box-sizing: border-box;
        border-right: 1px solid var(--bborder);
        border-bottom: 1px solid var(--bborder);

        &:first-child {
            border-left: 1px solid var(--bborder);
        }
    }

    .days li {
        height: 150px;
        overflow-y: auto;

        &:hover {
            background: #d3d3d3;
        }
    }

    .date {
        text-align: center;
        margin-bottom: 5px;
        font-size: 0.7rem;
        color: #333;
        float: right;
    }

    .event {
        clear: both;
        display: block;
        font-size: 13px;
        border-radius: 4px;
        padding: 5px;
        margin-top: 5px;
        background: #e4f2f2;
        border: 1px solid #b5dbdc;
        color: #009aaf;
        text-decoration: none;
    }

    .event-desc {
        color: #666;
        margin: 3px 0 7px 0;
        text-decoration: none;
        overflow: hidden;
    }

    .event-time {
        font-size: 0.7rem;
    }

    .day {
        background: #fff;
        color: #666;

        &.other-month {
            background: #dfdfdf;
        }
    }

    &.m-calendar-mini {
        .days li {
            height: auto;
        }
    }

    .has-event {
        font-weight: bold;
        background: #009aaf;
    }
}

@media(max-width: 768px) {
    .m-calendar {
        .weekdays, .other-month {
            display: none;
        }

        li {
            height: auto !important;
            border: 1px solid var(--bborder);
            width: 100%;
            padding: 10px;
            margin-bottom: -1px;
        }

        .date {
            float: none;
        }
    }
}