The Convert Date String to Quadword routine converts an absolute
    date string into an OpenVMS internal format date-time quadword.
    That is, given an input date/time string of a specified format,
    LIB$CONVERT_DATE_STRING converts this string to an OpenVMS
    internal format time.

    Format

      LIB$CONVERT_DATE_STRING  date-string ,date-time

                               [,user-context] [,flags] [,defaults]

                               [,defaulted-fields]

1  –  Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

2  –  Arguments

 date-string

    OpenVMS usage:time_name
    type:         character-coded text string
    access:       read only
    mechanism:    by descriptor

    Date string that specifies the absolute time to be converted
    to an internal system time. The date-string argument is the
    address of a descriptor pointing to this date string. This string
    must have a format corresponding to the currently defined input
    format, or it must be one of the relative day strings YESTERDAY,
    TODAY, or TOMORROW, or their equivalents in the currently
    selected language.

 date-time

    OpenVMS usage:date_time
    type:         quadword (unsigned)
    access:       write only
    mechanism:    by reference

    Receives the converted time. The date-time argument is the
    address of an unsigned quadword that contains this OpenVMS
    internal format converted time.

 user-context

    OpenVMS usage:context
    type:         longword (unsigned)
    access:       modify
    mechanism:    by reference

    Context variable that receives the translation context
    from a call to LIB$INIT_DATE_TIME_CONTEXT and then
    retains the translation context over multiple calls to
    LIB$CONVERT_DATE_STRING. The user-context argument is the address
    of an unsigned longword that contains this context. The user
    program should not write directly to this variable once it is
    initialized.

    The user-context parameter is optional. However, if a context
    cell is not passed, the routine LIB$CONVERT_DATE_STRING may
    abort if two threads of execution attempt to manipulate the
    context area concurrently. Therefore, when calling this routine
    in situations where reentrancy might occur, such as from AST
    level, VSI recommends that users specify a different context cell
    for each calling thread.

 flags

    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       read only
    mechanism:    by reference

    Specifies which date or time fields of the date-string argument
    might be omitted so that default values are applied. The flags
    argument is the address of a longword bit mask that contains
    these flags. A set bit indicates that the field may be omitted.
    The bit definitions for the mask correspond to the fields in a
    $NUMTIM "timbuf" structure as follows:

    Field           Bit Number  Mask

    Year            0            1
    Month           1            2
    Day of month    2            4
    Hours           3            8
    Minutes         4           16
    Seconds         5           32
    Fractional      6           64
    seconds

    Bits 7 through 31 must be zero and are Reserved for use by VSI. If
    this parameter is omitted, a default value of 120 (78H) is used,
    indicating that the time fields may be defaulted but the date
    fields may not.

 defaults

    OpenVMS usage:vector_word_unsigned
    type:         word (unsigned)
    access:       read only
    mechanism:    by reference, array reference

    Supplies the defaults to be used for omitted fields. The defaults
    argument is the address of an array of unsigned words containing
    these default values. This array corresponds to a 7-word $NUMTIM
    "timbuf" structure. If the defaults argument is omitted, the
    following defaults are applied:

    o  For the date group, the default is the current date.

    o  For the time group, the default is 00:00:00.00.

 defaulted-fields

    OpenVMS usage:mask_longword
    type:         longword (unsigned)
    access:       write only
    mechanism:    by reference

    Indicates which date or time fields have been defaulted. The
    defaulted-fields argument is the address of a longword bit mask
    that specifies these fields. The bit definitions are identical to
    those of the flags bit mask. A set bit indicates that the field
    was defaulted. Bits 7 through 31, which are reserved for use by
    VSI, are zeroed.