Rust Helpers

The Rust crate provides backend-friendly date helpers and string-serializable semantic date types. It intentionally leans on chrono for concrete instants and dates, while adding Lona/Tento domain shapes such as PartialDate.

Public Modules

• date_unit models calendar-scale units.
• datetime_range and naive_date_range add range helpers.
• naive_date_ext extends chrono::NaiveDate.
• partial defines PartialDate and SemanticTime.
• year, year_month, and year_month_day provide small calendar value helpers.

The crate re-exports:

pub use naive_date_range::NaiveDateRangeExt;
pub use partial::{PartialDate, SemanticTime};

Helper Constructors

src/lib.rs exposes concise constructors used in tests and backend code:

• naivedate("2026-04-29") parses a chrono::NaiveDate.
• utc_datetime(nd) turns a date into midnight UTC.
• current_milliseconds() returns epoch milliseconds.
• partial_date("ym-2026-04") parses a PartialDate.
• semantic_time("ymd-2026-04-29") creates a range-like SemanticTime.
• datetime("2026-04-29T18:30:00Z") parses a UTC datetime.

Use fallible parsing directly in request handlers when user input can be invalid. The helper constructors unwrap and are best for trusted inputs, tests, and fixtures.

PartialDate

Rust PartialDate supports the same semantic shapes as TypeScript:

PartialDate::Y(2026)
PartialDate::Ym(YearMonth { yr: 2026, mth1: 4 })
PartialDate::Ymd(naivedate("2026-04-29"))
PartialDate::Yw { yr: 2026, week: 18 }

start() and end() return the inclusive start and exclusive end date for the bucket. iter_weeks, iter_months, and iter_years produce adjacent partial date pairs for range-oriented callers.

SemanticTime

SemanticTime is either:

• Range(PartialDate) for imprecise calendar buckets;
• Point(DateTime<Utc>) for exact instants.

It serializes as a string and deserializes by trying RFC 3339 first, then PartialDate. Legacy pt- prefixed point strings are still accepted for backward compatibility.

Use SemanticTime in API models only when the field genuinely accepts both bucket-level and point-in-time values. Otherwise choose PartialDate, NaiveDate, or DateTime<Utc> directly.