The DJIA crossed above 15,000 for the first time ever today, but it has since fallen back below that level in afternoon trading. Whether or not the index will finish the day above that key threshold is unknown, but as of today it has been 2,115 days since the DJIA last crossed and closed above a thousand-point threshold for the first time.
In the table below, we list the first day that the DJIA closed above each thousand-point threshold from 1,000 to 14,000. Given the law of large numbers, with each thousand point threshold crossed, the percentage gain needed to cross the next threshold declines. For this reason, the amount of time that has elapsed between 14,000 and 15,000 is even more noteworthy. To get from 2,000 to 3,000, the DJIA rallied 50% in the span of 1,560 days. To get from 14,000 to 15,000, though, the DJIA only needed to rally a little over 7% -- but it still hasn't been able to do so after more than 2,000 days.
In the above chart it is also interesting to note how minor the 1987 crash now looks more than 25 years later. While the drops from 2000-02 and 2007-09 still look daunting in the chart, we can only hope that 25 years from now the DJIA has risen enough that those declines look like nothing more than a small blip.