It looks like at least some of the entries are already timestamped, here is an example
2012-12-09 06:28:26,041 - softwarecenter.ui.gtk3.app - INFO - software- center-agent finished with status 0 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1088343 Title: please timestamp entries in .xsession-errors To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg-server/+bug/1088343/+subscriptions -- ubuntu-bugs mailing list [email protected] https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
