.ucolick.org/~sla/leapsecs/timescales.html">Time
Scales</a> describes astronomical time scales like
<abbr title="Terrestrial Dynamic Time">TDT</abbr>,
<abbr title="Geocentric Coordinate Time">TCG</abbr>, and
<abbr title="Barycentric Dynamic Time">TDB</abbr>.
<li>The <a href="https://www.iau.org"><abbr
title="International Astronomical Union">IAU</abbr></a>’s <a
href="https://www.iausofa.org"><abbr
title="Standards Of Fundamental Astronomy">SOFA</abbr></a>
collection contains C and <a
href="https://en.wiki