As of Nov 2015, Oracle decided to change the naming method for PSU (Patch Set Update).
Before Nov 2015, the product PSU was represented by the last number in the 5 number format which increased with every PSU release (188.8.131.52.0 for the base release, 184.108.40.206.1 for the first PSU, 220.127.116.11.2 for the second and so on). Now, the last number in the format will be the release date of the PSU in the format YYMMDD. For example, the Jan 2016 PSU for 11.2 will not be 18.104.22.168.9 (22.214.171.124.8 was the previous one), but 126.96.36.199.160119, as it was release on Jan 19th 2016.
Note that all PSU of the same product and quarter will have the same name (even if they won’t be release on the same exact date). So it makes it much easier to see if we are up to date. It is difficult to know if 188.8.131.52.10 is the current one, but it’s easy to know that 184.108.40.206.160119 is.
This information is from MOS note# 2061926.1