The main Advent
Advent is the period before Christmas used by churchgoers to prepare for the coming of Jesus. It starts on the fourth Sunday before Easter and finishes on Christmas Day and many churches have an Advent wreath holding a set of four candles and they light the first candle on the first Sunday of Advent, the first and the second on the second Sunday of Advent and so on until they’re all burning.
Advent calendars should start on the first Sunday of Advent which varies from the 27th of November to the 3rd of December but most begin on 1 December instead (which is practical because it allows them to have the same number of windows each year).
Advent used to be a period of fasting and penitence but that certainly wouldn’t work in modern Australia with all those office parties and end of year break-ups. (Mind you, there must be some penitence when people remember what they did at last night’s party.)
An Advent custom you will not want to revive (unless you hate kids) is the Norman one of employing children under the age of twelve to run through fields and orchards with burning torches and set fire to bundles of straw (supposedly to get rid of vermin but perhaps it was also a method of population control for humans).
If you’re into liturgical colours, Advent is purple (except where it’s blue).
 And with a daily dose of chocolate from your advent calendar.