The help is as follows:
$ wee_reports --help
Usage: wee_reports: [config_file] [timestamp] [--config=CONFIG_FILE] [--help]
Run all reports defined in the specified configuration file. Use this utility
to run reports immediately instead of waiting for the end of an archive
interval.
Options:
-h, --help show this help message and exit
--config=CONFIG_FILE Use the configuration file CONFIG_FILE
But I have no idea, and it doesn't give a clue, nor does the documentation, about what format a timestamp should be in.