So when on the calendar is the shortest day of the year? ( For the Southern Hemisphere )

Is it in fact June 21st? Or is it the 22nd now, due to precession or the falling gold price?

This may sound like a simple question but to understand what you are asking is actually quite complicated.

The problem is that the calendar is a man-made invention but the motion of the solar system was set up by a completely different Agency, who did not mind using fractions of a day when He determined the length of the year. In the Gregorian calendar we don't use fractions of a day, so certain feasts and events move around. Like Easter. And Solstices. And Equinoxes.

The shortest day happens around the time when the sun reaches its furthest position north of the equator. In the year 2000 this happens at about 01.48 Universal Time on Wednesday June 21st. Not every year is the same. This date will move one or two days before or after June 21st for the same reason that we have an extra day in leap years. So it could happen from June 19th to June 23rd in any year. When we talk about "what day is it?" we have to take into account the International Date Line and the line on the earth directly opposite the sun, where it is "midnight". The area to the east of "midnight" is a day ahead of the area to the west of "midnight" - except when "midnight" crosses the International Date Line, when the whole world is on the same "day".

So when we say the solstice is at 01.48 UT on Wednesday 21st June, it is not "Wednesday" in the whole world. In fact in the USA, it is still Tuesday and for them the solstice occurs on Tuesday 20th June this year. In other years it may occur on the same "day" in the USA as it does in South Africa. But because there are always two "days" running at the same time at different places around the world (except when it is "midnight" across the International Date Line, when the whole world is on the same "day") we must be careful about noting a "day" for events that happen out in space.

For instance, Neil Armstrong may have landed on the moon on July 20th, for Americans, but it was July 21st for some other countries around the world. That is why, when you are talking about international events, it is good to define the reference system you are using. When you refer to the time and date of astronomical events you very definitely need to state what your reference system is.

And the international standard is now Universal Time ( the old Greenwich Mean Time ).

No matter what the gold price is.

Brian Fraser.