Native API online documentation, based on the System Informer (formerly Process Hacker) phnt headers
#ifndef _NTSAM_H

typedef struct _LOGON_HOURS
    USHORT UnitsPerWeek;

    // UnitsPerWeek is the number of equal length time units the week is
    // divided into. This value is used to compute the length of the bit
    // string in logon_hours. Must be less than or equal to
    // SAM_UNITS_PER_WEEK (10080) for this release.
    // LogonHours is a bit map of valid logon times. Each bit represents
    // a unique division in a week. The largest bit map supported is 1260
    // bytes (10080 bits), which represents minutes per week. In this case
    // the first bit (bit 0, byte 0) is Sunday, 00:00:00 - 00-00:59; bit 1,
    // byte 0 is Sunday, 00:01:00 - 00:01:59, etc. A NULL pointer means
    // DONT_CHANGE for SamSetInformationUser() calls.

    PUCHAR LogonHours;


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This type is documented in the [MS-SAMR] specification.