Know a keyframe's exact time on timeline

Somthing like this:

Get Key Index From Time/Frame:

target = thisComp.layer("Shape Layer 1").position;
frame = 60;
// or 
// frame = timeToFrames(2);
result = 'not found';
for (i = 1; i <= target.numKeys; i++) {
  if (timeToFrames(target.key(i).time) == frame) {
    result = 'key: ' + i;
    break
  }
}
result

Get Key Time From From Key Index:

target = thisComp.layer("Shape Layer 1").position;
if (target.numKeys) {
  numKey = 2;
  target.key(numKey).time + 's';
  // or
  // timeToFrames(target.key(numKey).time) +' frames';
} else {
  'no keyframe'
}