From what I've been able to figure out, we are not to try to predict the day, but to be watchful and aware of what is happening. Like being aware of the time of day or the season. When we see certain events come to pass, we have an awareness of where we are on the Biblical timeline.
Many predicted events have come to pass, Israel being the most obvious, but many others have not come to pass for us to be in the Rapture?
My understanding is that the Tribulation period begins with the signing of the peace treaty between the anti-christ and Israel. The rapture is believed to happen sometime in that time period.
The Left Behind series gives a good overview of what is the commonly accepted sequence of events for the whole thing.
The books are not the best written, and there’s a lot of rehashing of previous material in the later books. IMO, they could have cut the series down by about two books worth if they didn’t have so many flashbacks. However, they do present the whole rapture and tribulation period in a format that makes it easier to remember what is supposed to happen and when. The first book is pretty good. Books 2-4 are dry, and the series really gets going at book 5.
I tend to think along the lines that the rapture is a good explanation for a catastrophic event that solidifies the antichrists grab for power. It would be a good excuse to impose martial law for example, to control the chaos that would ensue.
The fact that we are witnessing, in our time, those signs being fulfilled almost daily is proof that the time of the Tribulation is very nearly here. Scripture tells us that the Rapture will occur before the Tribulation, so, since we are seeing the signs of the Tribulation being fulfilled before our very eyes, then the Rapture has to occur very soon.