Interval unit is days

If the interval unit for a calendar frequency is set to days (enumeration value of 3), and the offset start and offset start unit configured for this frequency is not null, then the first sample for a week is offset from the midnight of the Sunday of that week. The offset is generated using a value in the offset_start and offset_start_unit configured for that frequency. If the interval time between samples goes past the end of Saturday (that is, 11:59:59pm) of that week, then the first sample for the following week is again offset from the midnight (Sunday, 12:00am) of the following week.