Return the maximum length that a timezone abbreviation can have.
This can be used to fetch the appropriate number of characters
from a string during parsing in order to identify a possible
timezone entry.
Return one or more timezones for the given timezone abbreviation.
Examples are GMT for Greenwich Mean Time or
PST for Pacific Standard Time.
Note that there is RFC for these abbreviations, which means that
some of them resolve to multiple different timezones. Hence this
function will return multiple [[generated::Abbreviation]] items.