Happy New Year everybody 
I have a simple “historical” question about Swi-Prolog: in the website one reads “since 1987…etc etc”, but more recently I happened to read one of those “Did you know” messages on the left top of the site and I was quite surprised to see that “Did you know? Swi-Prolog is 28 years old” (which would mean it was born in 1995, not 1987). So the question is: how old is Swi-prolog? And why those two different dates? Thanks
I guess the DYK message should be rephrased. I always keep 1987 as the epoch. I do not really recall whether that was when I started or when the fist public release came out. Version control systems were not yet popular, surely not in academics. At some point I started using RCS. In 1992 I was pointed as CVS and started fresh. When the project was switched to GIT, the old history was preserved. So, you can get back to 1992. There were several import problems, so the code probably will not be in the exact state it was back then.
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Thanks. I like the use of acronyms because I usually get only the half of what they mean 
What do RCS and CVS mean? That have something to do with version control systems? BTW Thanks
You should probably google it, add “version control” to the search phrase. Those are version control systems from around that time. There was also one called SVN which was supposed to be a better CVS but Git appeared maybe 5 years later and suddenly most other solutions felt obsolete.
This is of course unfair, every tool has made some conscious or accidental trade-offs. You could for example check out this page that compares Git to Fossil. Surely there are similar articles about the other Git alternatives. Git is so dominant (popular) that you must explain yourself in great detail if you dare develop anything else 
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