:root {
  --md-admonition-icon--calendar
: url('data:image/svg+xml;charset=utf-8,<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><path d="M15 13h1.5v2.82l2.44 1.41-.75 1.3L15 16.69zm4-5H5v11h4.67c-.43-.91-.67-1.93-.67-3a7 7 0 0 1 7-7c1.07 0 2.09.24 3 .67zM5 21a2 2 0 0 1-2-2V5c0-1.11.89-2 2-2h1V1h2v2h8V1h2v2h1a2 2 0 0 1 2 2v6.1c1.24 1.26 2 2.99 2 4.9a7 7 0 0 1-7 7c-1.91 0-3.64-.76-4.9-2zm11-9.85A4.85 4.85 0 0 0 11.15 16c0 2.68 2.17 4.85 4.85 4.85A4.85 4.85 0 0 0 20.85 16c0-2.68-2.17-4.85-4.85-4.85"/></svg>')
}
.md-typeset .admonition.calendar,
.md-typeset details.calendar {
  font-size:1.5rem;
  display:flex;
  justify-content:center;
  border-color: yellow;
}
.md-typeset .calendar > .admonition-title,
.md-typeset .calendar > summary {
  background-color: transparent;
}
.md-typeset .calendar > .admonition-title::before,
.md-typeset .calendar > summary::before {
  background-color: yellow;
  -webkit-mask-image: var(--md-admonition-icon--calendar
);
          mask-image: var(--md-admonition-icon--calendar
        );
}