If you are talking about working out the downtime of your server then I would suggest setting up 2 crone jobs. One crone job occurs every minute and the other once a day all year round. The job that occures every minute will append to a mysql database that the server is still running. Then the job that occures once a day will use that data to spot any gaps of when the server did not append anything to the mysql database which will then submit the daily report to another database while clearing the entries in the database that is appended to every minute. But you will need to be carefull when setting up this sort of crone job so that you don't slow down the server. That bit of theory should explain.