Function format_rfc3339 

pub fn format_rfc3339(instant_ns: i64) -> String

Format a SmoothUTC instant as an RFC 3339 / ISO 8601 UTC timestamp (Z zone), e.g. 1970-01-01T00:00:00Z or 2024-03-10T07:30:00.123456789Z. Sub-second precision appears only when nonzero, with trailing zeros trimmed.