No one said the 6-day were each 24-hour day, YoursTrue, because Genesis never said anything about hours.
But what it does say that each day in Genesis 1, as "evening and morning", which equate to a day.
The start of evening varied (due to rotation and tilting of the Earth would cause day lasting longer or shorter, depending on the hemisphere that you lived in, so at winter solstice, daylight is shorter in December and summer solstice is longer, for those living in the northern hemisphere). As ancient people don't have clocks, the start of new day usually start at sunrise or sunset, but for Jews, it start at sundown.
The day is certainly not "a thousand years", as some Christians claim (because of 2 Peter 3:8), because Genesis 1 say nothing about a year, let alone a thousand years.
But the true meaning or true value to the Creation story isn't about creation at all (and it is about science or history), but the Hebrew belief that the sabbath - the day of rest - is a holy day in a 7-day week.
Genesis Creation (6-day creation) is merely a parable or allegory for the law and rite of sabbath (Exodus). Christians have to tendency to forget this, why there are 7-day week and the last day is a day of rest.