trilium/apps/client/stylesheets/calendar.css

.calendar-dropdown-widget *,
.calendar-dropdown-widget *:before,
.calendar-dropdown-widget *:after {
    box-sizing: border-box;
}

.calendar-dropdown-widget {
    margin: 0 auto;
    overflow: hidden;
    width: 100%;
}

.calendar-dropdown-widget .calendar-btn {
    -moz-user-select: none;
    -ms-user-select: none;
    user-select: none;
    -webkit-appearance: button;
    appearance: none;
    background: none;
    border: 0;
    color: inherit;
    cursor: pointer;
    font-size: x-large;
    line-height: normal;
    min-width: 27px;
    outline: none;
    overflow: visible;
    padding: 0;
    text-align: center;
}

.calendar-dropdown-widget .calendar-header {
    align-items: center;
    display: flex;
    padding: 0 0.5rem 0.5rem 0.5rem;
}

.calendar-dropdown-widget .calendar-header>div {
    display: flex;
    justify-content: center;
    flex-grow: 1;
}

.calendar-dropdown-widget .calendar-header input[type="number"] {
    appearance: textfield !important;
}

.calendar-dropdown-widget .calendar-header input[type="number"]::-webkit-outer-spin-button,
.calendar-dropdown-widget .calendar-header input[type="number"]::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

.calendar-dropdown-widget .calendar-header select {
    cursor: pointer;
}

.calendar-dropdown-widget .calendar-header input,
.calendar-dropdown-widget .calendar-header .dropdown-toggle {
    appearance: none;
    text-align: center;
    border: 0;
    border-left: unset;
    background-color: var(--menu-background-color);
    font-weight: bold;
    outline: 0;
}

.calendar-dropdown-widget .calendar-header .dropdown-toggle::after {
    border: unset;
    /* Disable the dropdown arrow */
}

.calendar-dropdown-widget .calendar-week {
    display: flex;
    flex-wrap: wrap;
}

.calendar-dropdown-widget .calendar-week span {
    flex-direction: column;
    flex: 0 0 12.5%;
    font-size: 1rem;
    font-weight: bold;
    max-width: 12.5%;
    padding-top: 5px;
    padding-bottom: 5px;
    text-align: center;
    text-transform: uppercase;
}

.calendar-dropdown-widget .calendar-body {
    display: flex;
    flex-wrap: wrap;
}

.calendar-dropdown-widget .calendar-week-number {
    color: var(--muted-text-color) !important;
    position: relative;
}

.calendar-dropdown-widget .calendar-week-number::after {
    content: '';
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    width: 1px;
    background-color: var(--main-border-color);
    z-index: 2;
}

.calendar-dropdown-widget .calendar-week-number-disabled {
    align-items: center;
    color: var(--main-text-color);
    display: flex;
    flex-direction: column;
    flex: 0 0 12.5%;
    max-width: 12.5%;
    padding: 0.4rem 0;
    font-size: 120%;
}

.calendar-dropdown-widget .calendar-date {
    align-items: center;
    color: var(--main-text-color);
    display: flex;
    flex-direction: column;
    flex: 0 0 12.5%;
    max-width: 12.5%;
    padding: 0.4rem 0;
    font-size: 120%;
}

.calendar-dropdown-widget .calendar-date:hover {
    color: var(--hover-item-text-color);
    background-color: var(--hover-item-background-color);
    text-decoration: underline;
}

.calendar-dropdown-widget .calendar-date-active {
    background-color: var(--active-item-background-color);
    color: var(--active-item-text-color);
}

.calendar-dropdown-widget .calendar-date-today {
    font-weight: bold;
}

.calendar-dropdown-widget a {
    text-decoration: none;
}

.calendar-dropdown-widget .calendar-date-exists {
    text-decoration: underline !important;
}

.calendar-dropdown-widget .calendar-date:not(.calendar-date-active) {
    cursor: pointer;
}

.calendar-dropdown-widget .calendar-date-prev-month,
.calendar-dropdown-widget .calendar-date-next-month {
    color: var(--muted-text-color);
    opacity: 0.6;
}

.calendar-dropdown-widget .calendar-date-prev-month:hover,
.calendar-dropdown-widget .calendar-date-next-month:hover {
    opacity: 1;
    background-color: var(--hover-item-background-color);
    color: var(--hover-item-text-color);
    text-decoration: underline;
}