Summer solstice 2020: Planets come out to play at end of longest day

Today is the longest day of the year. It also marks the start of summer.

Hang on, what about December 1?

Australia is one of just a few countries that considers December 1 the beginning of summer (or winter in the northern hemisphere), says astronomer Fred Watson.

“My understanding is that that comes from colonial times because it was the 1st of December when the troops got their summer uniforms and got out of their winter uniforms,” Professor Watson says.

Most of the rest of the world marks the start of summer (or winter) on the solstice.

Normally this happens on December 22, but this year was a leap year so it falls on December 21.