"az monitor activity-log list --start-time 2018-02-16T00:00:00-0800"
renders error
"time data '2018-02-16T00:00:00-0800' does not match format '%Y-%m-%dT%H:%M:%SZ'".
--end-time has the same issue.

Environment summary

Install Method: MSI / CLI version: 2.0.21 / OS version: Windows 10 / Shell Type: cmd.exe