853-855 Subfield $x - Calendar change:

Subfield $x contains one or more two- or four-character numeric codes that indicate the chronological point at which the highest level increments or changes.

Codes:  A two-character code identifies the month or season of change.  A four-character code in the pattern mmdd (2 for the month and 2 for the day) identifies the month and day of change.  A month or day code of less than two digits is right justified and the unused position contains a zero.

Examples:

853  23  $81$av.$bno.$u4$vr$i(year)$j(season)$wq$x21

[A quarterly publication for which issue no. 1 of each volume is identified as Spring.]

853  20  $81$av.$bno.$u12$vc$i(year)$j(month)$wm$x07

[A monthly publication consisting of 12 numbers per volume; the volume number increments in July.]

When there is more than one change in a year (for example, 12 numbers per year are issued as 2 volumes per year), all of the calendar change codes are contained in one subfield $x and the codes are separated by a comma.  Subfield $x is not related to a specific caption.  It is input following the last subfield.

Example:

853  22  $81$av.$bno.$u6$vc$i(year)$j(month)$wm$x06,12

[A monthly publication which has 6 numbers per volume.  The numbers increment continuously, and new volumes begin in June and December.]

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