Re: GW200105 and GW200115
Yes, you are right, you can make the system for ever with a tiny modification: just assume that the date is of the form <Y><M><D> where <M> & <D> are 2-digit strings, and <Y> is at least 4 digits. So then GW99929281370103/1474372828 was the 1474372828th event from 3 Jan 9992928137. It has problems with BCE events, but those could be fixed.
Knowing details about the event was what the tag field was for.
And, surprisingly enough, I can be very sure that GW20150914 was in fact from 14th September 2015 because I can read dates.
I have huge admiration for the GW detections, but not for this. For the cost of two characters they could have had a system which would compatibly extend indefinitely but instead they chose to make it so that every bit of software written to deal with these things after 2100 will need to have special cases for the early braindead naming scheme. Two characters.