Given an output format and language, the Retrieve the Maximum
    Length of a Date/Time String routine determines the maximum
    possible length for the date-string string returned by
    LIB$FORMAT_DATE_TIME.

    Format

      LIB$GET_MAXIMUM_DATE_LENGTH  date-length [,user-context]

                                   [,flags]

1  –  Returns

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

2  –  Arguments

 date-length

    OpenVMS usage:longword_signed
    type:         longword (signed)
    access:       write only
    mechanism:    by reference

    Receives the maximum possible length of the date-string argument
    returned to LIB$FORMAT_DATE_TIME. The date-length argument is the
    address of a signed longword that receives this maximum length.
    The length written to date-length reflects the greatest possible
    length of an output date/time string for the currently selected
    output format and natural language.

    For example, if the selected output date/time format includes
    the alphabetic, unabbreviated month name (assuming English as
    the natural language), the longest month name (September) would
    have to be taken into consideration when determining the maximum
    possible length of date-string.

 user-context

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

    Context variable that retains the translation context over
    multiple calls to this routine. The user-context argument is the
    address of an unsigned longword that contains this context. The
    initial value of the context variable must be zero. Thereafter,
    the user program must not write to the cell.

    The user-context parameter is optional. However, if a context
    cell is not passed, the routine LIB$GET_MAXIMUM_DATE_LENGTH
    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

    Bit mask that allows the user to specify whether the date, time,
    or both are to be included in the calculation of the maximum date
    length. The flags argument is the address of an unsigned bit mask
    containing the specified values. Valid values are LIB$M_DATE_
    FIELDS and LIB$M_TIME_FIELDS. The values specified for flags must
    correspond to the flags argument passed to LIB$FORMAT_DATE_TIME.