Stop estimating. I have analysed every team I have been on that use estimation. Those teams have been 99% incorrect. In my experience, it does not work. If you need dates, I would recommend a more modern approach like forecasting.
What's the difference between estimating and forecasting? Seems very binary as written, but at some point don't you have to look forward and make some assumptions on complexity/effort required to solve a problem and the general time it takes to solve them in order to do a forecast?