Transits
What the sky is doing to your chart
Where the planets are now against where they were when you were born. This is the technique a horoscope approximates: given a birth time it uses your actual houses rather than counting from your Sun sign, and every date is the exact moment the aspect perfects.
How this works
What a transit is
Your birth chart is a snapshot and it never changes. The sky does. A transit is a planet moving into an exact angle with something in that snapshot: Saturn arriving at the degree your Sun occupies, or Jupiter reaching the point 120 degrees from your Moon.
That is why transits are dated and horoscopes are not. There is one moment when the angle is exact, and it can be calculated to the minute for any year you like.
Why some happen three times
A slow planet crosses the point, turns retrograde and passes back over it, then turns direct and crosses a third time. It can take most of a year. The tradition treats that as one episode with three peaks rather than three separate events, and the readings above are grouped that way rather than listing the same transit three times.
What the birth time changes
Not the dates. Those come from your birth date and are the same either way. It changes the houses, which is to say the area of life a transit lands in, and there is no way to work that out without one.
Every Sun-sign horoscope on the internet, including the ones on this site, gets around that by counting houses from your Sun sign. It is a real technique and it is an approximation. Where no birth time is given here, the houses are withheld rather than approximated, because presenting the substitute as the real thing is how a tool stops being worth trusting.
The rest of the picture
A transit list is most useful beside the chart it is transiting. All of these are free and computed from the same ephemeris.