Users can specify a day of month upon which their data usage
resets. Internally, cycle boundaries are defined to end at midnight
(00:00) UTC on the requested day. When a month is shorter than the
requested day, the cycle resets on the first day of the subsequent
month. For example, a cycle reset day of the 30th would cause a reset
on January 30 at 00:00 UTC and March 1 at 00:00 UTC.