I was looking for a particular spring-web version in my local Maven repo and found quite a few and then went on to look for spring-core versions to find this:
118658 markus 20080602 ./spring-core/1.2.6/spring-core-1.2.6.jar
169450 markus 20081001 ./spring-core/2.0/spring-core-2.0.jar
172430 markus 20070606 ./spring-core/2.0.1/spring-core-2.0.1.jar
173719 markus 20070731 ./spring-core/2.0.2/spring-core-2.0.2.jar
178417 markus 20070606 ./spring-core/2.0.3/spring-core-2.0.3.jar
179193 markus 20080507 ./spring-core/2.0.4/spring-core-2.0.4.jar
180362 markus 20070607 ./spring-core/2.0.5/spring-core-2.0.5.jar
180002 markus 20080923 ./spring-core/2.0.6/spring-core-2.0.6.jar
182534 markus 20080110 ./spring-core/2.0.7/spring-core-2.0.7.jar
182184 markus 20100921 ./spring-core/2.0.8/spring-core-2.0.8.jar
270968 markus 20100303 ./spring-core/2.5/spring-core-2.5.jar
284876 markus 20080511 ./spring-core/2.5.3/spring-core-2.5.3.jar
285801 markus 20090829 ./spring-core/2.5.4/spring-core-2.5.4.jar
287235 markus 20081022 ./spring-core/2.5.5/spring-core-2.5.5.jar
285603 markus 20090629 ./spring-core/2.5.6.SEC01/spring-core-2.5.6.SEC01.jar
285491 markus 20090629 ./spring-core/2.5.6/spring-core-2.5.6.jar
359338 markus 20100119 ./spring-core/3.0.0.RELEASE/spring-core-3.0.0.RELEASE.jar
367170 markus 20100917 ./spring-core/3.0.4.RELEASE/spring-core-3.0.4.RELEASE.jar
382442 markus 20110524 ./spring-core/3.0.5.RELEASE/spring-core-3.0.5.RELEASE.jar
382184 markus 20140215 ./spring-core/3.0.6.RELEASE/spring-core-3.0.6.RELEASE.jar
383621 markus 20140927 ./spring-core/3.0.7.RELEASE/spring-core-3.0.7.RELEASE.jar
442400 markus 20140217 ./spring-core/3.1.0.RELEASE/spring-core-3.1.0.RELEASE.jar
449324 markus 20120825 ./spring-core/3.1.1.RELEASE/spring-core-3.1.1.RELEASE.jar
449649 markus 20140531 ./spring-core/3.1.2.RELEASE/spring-core-3.1.2.RELEASE.jar
879449 markus 20130314 ./spring-core/3.2.0.RELEASE/spring-core-3.2.0.RELEASE.jar
863642 markus 20130314 ./spring-core/3.2.1.RELEASE/spring-core-3.2.1.RELEASE.jar
866788 markus 20130526 ./spring-core/3.2.2.RELEASE/spring-core-3.2.2.RELEASE.jar
867800 markus 20140215 ./spring-core/3.2.3.RELEASE/spring-core-3.2.3.RELEASE.jar
872983 markus 20140217 ./spring-core/3.2.7.RELEASE/spring-core-3.2.7.RELEASE.jar
973502 markus 20140531 ./spring-core/4.0.3.RELEASE/spring-core-4.0.3.RELEASE.jar
Firstly I have this habit of copying the repo from one laptop to the next and sometimes between laptop and PCs, hence seven years of spring versions with gaps; Secondly, spring-core almost increased six times in in size between those versions.
It is also an indicator since when I have been using Spring with Maven : at least since mid 2007.
Martina and I were introducing Maven at our workplace at that time as part of a JPA / Struts2 project that was using Spring for IOC.
So on the same laptop I checked for the oldest jar:
498051 markus 20051123_052529 ./struts/struts/1.1/struts-1.1.jar
40 markus 20060208_104252 ./opensymphony/xwork/1.1.1/xwork-1.1.1.jar.sha1
Hmm, 2005. Not sure what that means.