Function format_date 

pub fn format_date(z: i64) -> String

Canonical openCypher ISO rendering of a date (YYYY-MM-DD). Years 0000–9999 are zero-padded to four digits with no sign; outside that range the ISO-8601 expanded form applies — a leading + for years > 9999 and - for negative years (Neo4j: “a plus sign must prefix any year after 9999”). Matches chrono’s %Y for the years chrono can render, and extends past chrono’s ±262k cap.