rrdtool lastupdate

A variety of tools use RRD databases which are ideal for recording a sequence of values over time. So one interesting question is when the last time the rrd file was updated - rrdtool's lastupdate mode will tell you.

$ rrdtool lastupdate probe302Value_probe302Value.rrd
1334603585: 190.0

The most recent value in the RRD is 190.0 recorded at 1334603585

The value of the time is a UTC timestamp. Converting this value to a readable date/time can be performed using the UN*X date command.

$ date -d '@1334603681'
Mon Apr 16 15:14:41 EDT 2012

With knowing the last update and most recent value you can verify that the database is being updated at the correct interval and with the expected values.