since the first large group of non-English Wikipedias came online.
Originally with spelled-out names rather than language codes, these
(deutsche and catalan had been created earlier that year)
The idea of having Wikipedias in multiple languages came from Jimbo in
March 2001 (http://lists.wikimedia.org/
note that the original German Wikipedia was actually set up at that
time, making it the second-oldest Wikipedia. Though the idea of using
two-letter domain codes was first raised then, after the above sites
were brought online in May there was further discussion, and the sites
were switched to two-letter codes a few days later:
Wikipedia Argentina also celebrated the es:wp10th anniversary today.
Happy tenth birthday, Wikipedias! (and many more!) May all of our
language editions flourish.