datetime - How to describe repeating intervals which has an unfixed time interval in ISO 8601? -

For example, for a fixed time interval format, we will call " 30 9 * * * "With " (Crontab time format) "> R / 2015-03-01 T 9: 30: 00-06: 00 / P1D "> ISO 8601 ).

But in ISO 8601, " 10, 2,4,6,8,10,14,18,22 * * * " (which is an unpublished time lag) How can I describe?

Thanks a lot!