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The above sections suggest to use ‘oldest possible’ archive format if in doubt. However, sometimes it is not possible. If you attempt to archive a file whose metadata cannot be represented using required format, GNU tar will print error message and ignore such a file. You will than have to switch to a format that is able to handle such values. The format summary table (see Formats) will help you to do so.
In particular, when trying to archive files larger than 8GB or with
timestamps not in the range 1970-01-01 00:00:00 through 2242-03-16
12:56:31 utc, you will have to chose between GNU and
POSIX archive formats. When considering which format to
choose, bear in mind that the GNU format uses
two's-complement base-256 notation to store values that do not fit
into standard ustar range. Such archives can generally be
read only by a GNU tar implementation. Moreover, they sometimes
cannot be correctly restored on another hosts even by GNU tar. For
example, using two's complement representation for negative time
stamps that assumes a signed 32-bit time_t generates archives
that are not portable to hosts with differing time_t
representations.
On the other hand, POSIX archives, generally speaking, can be extracted by any tar implementation that understands older ustar format. The only exception are files larger than 8GB.