Constant REASONABLE_PIECES_LEN 

const REASONABLE_PIECES_LEN: usize = 73;

Defines the “maximum” possible length (in bytes) of an RFC 9557 zoned datetime via the “pieces” API.

This generally should be identical to REASONABLE_ZONED_LEN, except its expected maximum is one byte longer. Namely, the pieces API currently lets the caller roundtrip the “criticality” of the timestamp. i.e., the ! in the time zone annotation. So it’s one extra byte longer than zoned datetimes.

Note that all the same considerations from variable length IANA tzdb identifiers apply to the pieces printing just as it does to zoned datetime printing.