The winter solstice – the shortest day

Sunset on 29 August 2005 as seen from Sydney Observatory, image Nick Lomb

Melissa asks:

Something that bothers me every year is this: which day actually has the shortest day and the longest night (or v-v), eg is it sundown prior to the solstice to sunup just after the solstice which is the longest night? Eg is tonight (21st June) the longest night (southern hemisphere), whereas tomorrow is the shortest day?

And also, there is much calendar confusion re the solstice day (21 or 22). Is that because in Australia we are closer to the dateline and thus it is 22nd here at the point of solstice whereas it is still the 21st in the US (where so many of our calendars originate)? Thus you get the apparent paradox of winter solstice here being a different calendar day to summer solstice there. Have I understood this correctly?

This year winter solstice, which is the time the Sun is at its furthest north for the year, occurs at 4:06 am Australian Eastern Standard Time on Friday 22 June 2007. That means that Friday is the shortest day. Since the solstice occurs during the night of 21/22 June that is the longest night.

As most of the world apart from New Zealand is behind Australian time, in the time zones of countries like the UK and the USA the solstice occurs the day before that in Australia. Hence there is confusion for some people who have calendars with information sourced from overseas and who consequently think that the solstice and the shortest day are today. I should also point out that though from Friday onwards the days will start to get longer, the differences initially from day to day are only a few seconds and hence not noticeable.

And Sarah McDonald on ABC702 please note that the earliest sunset for the year did not occur on the solstice, but about 10 days earlier. Similarly, the latest sunrise will not be on the day of the solstice, but about 10 days later. The explanation for this involves the esoteric concept of the equation of time, but that is another story or blog post…..