Not all date/time outputs are localized per text.*.ini strings

The (plural) words "years", "months", "days", "hours", "minutes", and "seconds" are currently text strings, only used by sbbs_t::age_of_posted_item() There are no singular equivalents (e.g. for "1 hour"), or for week.

All other date/time and duration outputs that use words (e.g. @-codes) either use-coded English (e.g. duration_estimate_to_vstr()) single-letter abbreviations of English words (which might be fine), and assume adding an 's' is proper pluralization.