I did see the post here: How do I get sar to show for the previous day?
But it doesn't answer my questions below.
I am trying to use sar to look at the statistics from yesterday (March 9th):
$ sar -f /var/log/sa/sa09 Linux 2.6.32-431.el6.x86_64 ([hostname]) 02/09/2016 _x86_64_ (12 CPU)
I wonder why the date is Feb 9th instead of March 9th although the last modified date of the log is March 9th.
Another question is how come the statistics (from the command above) contain 48 hours of statistics? I thought the file (i.e. sa09) only contained 1 day of statistics.