When extracting a jar archive all the files have a timestamp with the time of their extraction. They should have a timestamp which is listed in the archive.

Example:

ts90276@cobra:~ $ jar tvf 119534-02.jar
   203 Tue May 10 17:53:50 CEST 2005 119534-02/prepatch
    76 Tue May 10 17:53:50 CEST 2005 119534-02/.diPatch
   181 Tue May 10 17:54:00 CEST 2005 119534-02/patchinfo
  2025 Fri Jun 03 08:53:06 CEST 2005 119534-02/README.119534-02
   646 Wed May 11 18:15:00 CEST 2005 119534-02/SUNWinst/pkgmap
   466 Wed May 11 18:15:00 CEST 2005 119534-02/SUNWinst/pkginfo
[...]

ts90276@cobra:~ $ ls -lR 119534-02
119534-02:
total 10
-rw------- 1 ts90276 staff 2025 Aug 12 10:55 README.119534-02
drwx--x--x 4 ts90276 staff 512 Aug 12 10:55 SUNWinst
-rw------- 1 ts90276 staff 181 Aug 12 10:55 patchinfo
-rw------- 1 ts90276 staff 203 Aug 12 10:55 prepatch

119534-02/SUNWinst:
total 8
drwx--x--x 2 ts90276 staff 512 Aug 12 10:55 install
-rw------- 1 ts90276 staff 466 Aug 12 10:55 pkginfo
-rw------- 1 ts90276 staff 646 Aug 12 10:55 pkgmap
drwx--x--x 3 ts90276 staff 512 Aug 12 10:55 reloc
[...]