$ rrdtool lastupdate probe302Value_probe302Value.rrdThe 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.
Text 1: The most recent value in the RRD is 190.0 recorded at 1334603585
$ date -d '@1334603681'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.
Mon Apr 16 15:14:41 EDT 2012
Text 2: Converting a timestamp to a date/time.