Mentioned this already in an answer to a related question. DateListPlot in Mathematica 10 has a horrible bug: If two points have the same time coordinate, only one is plotted; the others are ignored. This is different in Mathematica 9, where all points are plotted correctly. Wolfram tells me that they have this bug in their list to be fixed in the next update. For now I made a workaround with a function that makes identical time coordinates differ by a few seconds, so that DateListPlot plots all points. Has anybody another solution?
Here's my current workaround. Works only if the distinct time coordinates are sufficiently separated.