Enum Scale 

#[non_exhaustive]
#[repr(u8)]
pub enum Scale {
    TAI = 0,
    TT = 1,
    ET = 2,
    TDB = 3,
    UTC = 4,
    UtcSpice = 5,
    UtcHist = 6,
    GPS = 7,
    GST = 8,
    BDT = 9,
    QZSS = 10,
    TCG = 11,
    TCB = 12,
    LTC = 13,
    TCL = 14,
    Custom = 15,
}

Time scales supported by the library.

This #[non_exhaustive] enum defines all time scales that [Dt] can represent. Each [Dt] instance stores its internal time value on the scale indicated by its scale field.

UTC and Leap Seconds

The library supports three UTC variants:

• UTC — Modern UTC using the library’s built-in IERS leap second table. Basic functions for run-time loading of leap seconds tables also available.

• UtcSpice — SPICE-compatible model. Uses a fixed +9 s offset before 1972-01-01 and modern leap seconds afterward.

• UtcHist — Full historical SOFA model with piecewise linear frequency offsets (“rubber seconds”) from 1961–1972. This variant does not support round-tripping.

Scale Categories

Category	Scales	Purpose
Atomic / Proper	TAI, TT, TDB (alias ET)	Continuous atomic time. TAI is the primary internal scale.
Relativistic Coordinate	TCG, TCB, TCL	Time scales defined in specific relativistic reference frames (GCRS, BCRS, LCRS).
Civil / Coordinated	UTC, UtcSpice, UtcHist	Real-world civil time, with support for leap seconds and historical behavior.
GNSS / Navigation	GPS, GST, BDT, QZSS	Time scales used by satellite navigation constellations.
Lunar	LTC, TCL	Lunar time scales based on the LTE440 model (Lu et al. 2025).
Special	Custom	User-defined or experimental scales.

The reference epoch used for conversions between scales is 2000-01-01 12:00:00 TAI.

Lunar Time Scales

Both LTC and TCL implement the LTE440 model (Lu et al. 2025):

• LTC (Coordinated Lunar Time): Operational lunar time for cislunar operations. Applies a secular rate of +56.02 µs per Earth day relative to TT, plus the 13 dominant periodic terms from the model.

• TCL (Lunar Coordinate Time): IAU-defined relativistic coordinate time in the Lunar Celestial Reference System (LCRS). Includes the secular rate versus TDB, the same periodic terms, and a constant bias calibrated to match the published LTE440 reference value at J2000.0 TDB.

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

TAI = 0

International Atomic Time (TAI).

TT = 1

Terrestrial Time (TT).

A smooth, continuous atomic time scale used in astronomy and dynamics.

ET = 2

Ephemeris Time (alias for TDB).

TDB = 3

Barycentric Dynamical Time (TDB).

Used for planetary and spacecraft calculations.

UTC = 4

Coordinated Universal Time (UTC) using modern leap second rules.

UtcSpice = 5

Coordinated Universal Time using the SPICE historical model (fixed +9 s offset before 1972).

UtcHist = 6

Coordinated Universal Time using the full historical SOFA model (with “rubber seconds” between 1960–1972).

Round-tripping is not supported.

GPS = 7

GPS Time.

The time scale used by the U.S. GPS satellite navigation system.

GST = 8

Galileo Time.

The time scale used by Europe’s Galileo satellite navigation system.

BDT = 9

BeiDou Time.

The time scale used by China’s BeiDou satellite navigation system.

QZSS = 10

QZSS Time.

The time scale used by Japan’s QZSS satellite system (similar to GPS).

TCG = 11

Geocentric Coordinate Time (TCG).

A relativistic time scale centered on Earth, used for high-precision work near Earth (e.g. satellite orbits).

TCB = 12

Barycentric Coordinate Time (TCB).

A relativistic time scale for the entire solar system.

LTC = 13

Coordinated Lunar Time (LTC).

Operational lunar time scale intended for cislunar operations. Based on the LTE440 model.

TCL = 14

Lunar Coordinate Time (TCL).

Theoretical relativistic coordinate time at the Moon’s center of mass. Based on the LTE440 model.

Custom = 15

Custom / user-defined scale.

Implementations

impl Scale

pub const WIRE_SIZE: usize = 1

Size of the canonical wire representation in bytes.

pub const fn is_tai(&self) -> bool

Returns true if this scale is TAI.

pub const fn to_utc(&self) -> Scale

Converts this Scale to UTC.

• If the scale is already one of the UTC variants including historical UTC then no change occurs.

pub const fn uses_leap_seconds(&self) -> bool

Returns true if this scale accounts for leap seconds (or historical UTC civil time rules).

pub const fn is_gnss(&self) -> bool

Returns true if this scale is based off a GNSS constellation.

pub fn from_abbrev(s: &str) -> Option<Self>

Parse scale from abbreviation. Returns None for any non-ASCII input.

pub const fn abbrev(&self) -> &'static str

Short abbreviation used for formatting / display (e.g. “TAI”, “UTC”, “UtcSpice”).

pub const fn eq(self, other: Self) -> bool

Const-friendly equality comparison.

pub const fn from_u8(v: u8) -> Scale

Attempts to reconstruct a Scale from its wire byte representation.

• Returns Custom for any value that does not correspond to a known variant.
• This provides safe deserialization from untrusted sources.

pub const fn to_u8(self) -> u8

Returns the wire representation of this Scale as a single byte.

The returned byte is the repr(u8) discriminant of the enum. This is the canonical on-wire form used by [Dt].

Trait Implementations

impl Clone for Scale

fn clone(&self) -> Scale

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Copy for Scale

impl Debug for Scale

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Scale

fn default() -> Scale

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Scale

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for Scale

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Scale

impl Hash for Scale

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Scale

fn cmp(&self, other: &Scale) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl PartialEq for Scale

fn eq(&self, other: &Scale) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Scale

fn partial_cmp(&self, other: &Scale) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Serialize for Scale

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for Scale

impl Tsify for Scale

const DECL: &'static str = "/**\n * Time scales supported by the library.\n *\n * This `#[non_exhaustive]` enum defines all time scales that [`Dt`] can represent.\n * Each [`Dt`] instance stores its internal time value on the scale indicated by\n * its `scale` field.\n *\n * ## UTC and Leap Seconds\n *\n * The library supports three UTC variants:\n *\n * - **`UTC`** \u{2014} Modern UTC using the library\u{2019}s built-in IERS leap second table.\n * Basic functions for run-time loading of leap seconds tables also available.\n *\n * - **`UtcSpice`** \u{2014} SPICE-compatible model. Uses a fixed +9 s offset before\n * 1972-01-01 and modern leap seconds afterward.\n *\n * - **`UtcHist`** \u{2014} Full historical SOFA model with piecewise linear frequency\n * offsets (\\\"rubber seconds\\\") from 1961\u{2013}1972. This variant does **not support\n * round-tripping**.\n *\n * ## Scale Categories\n *\n * | Category | Scales | Purpose |\n * |-----------------------------|---------------------------------|---------|\n * | **Atomic / Proper** | `TAI`, `TT`, `TDB` (alias `ET`) | Continuous atomic time. `TAI` is the primary internal scale. |\n * | **Relativistic Coordinate** | `TCG`, `TCB`, `TCL` | Time scales defined in specific relativistic reference frames (GCRS, BCRS, LCRS). |\n * | **Civil / Coordinated** | `UTC`, `UtcSpice`, `UtcHist` | Real-world civil time, with support for leap seconds and historical behavior. |\n * | **GNSS / Navigation** | `GPS`, `GST`, `BDT`, `QZSS` | Time scales used by satellite navigation constellations. |\n * | **Lunar** | `LTC`, `TCL` | Lunar time scales based on the LTE440 model (Lu et al. 2025). |\n * | **Special** | `Custom` | User-defined or experimental scales. |\n *\n * The reference epoch used for conversions between scales is **2000-01-01 12:00:00 TAI**.\n *\n * ## Lunar Time Scales\n *\n * Both `LTC` and `TCL` implement the **LTE440** model (Lu et al. 2025):\n *\n * - **`LTC`** (Coordinated Lunar Time): Operational lunar time for cislunar operations.\n * Applies a secular rate of **+56.02 \u{b5}s per Earth day** relative to TT, plus the\n * 13 dominant periodic terms from the model.\n *\n * - **`TCL`** (Lunar Coordinate Time): IAU-defined relativistic coordinate time\n * in the Lunar Celestial Reference System (LCRS). Includes the secular rate\n * versus TDB, the same periodic terms, and a constant bias calibrated to match\n * the published LTE440 reference value at J2000.0 TDB.\n */\nexport type Scale = \"TAI\" | \"TT\" | \"ET\" | \"TDB\" | \"UTC\" | \"UtcSpice\" | \"UtcHist\" | \"GPS\" | \"GST\" | \"BDT\" | \"QZSS\" | \"TCG\" | \"TCB\" | \"LTC\" | \"TCL\" | \"Custom\";"

const SERIALIZATION_CONFIG: SerializationConfig

type JsType = JsType

fn into_js(&self) -> Result<Self::JsType, Error>

where Self: Serialize,

fn from_js<T>(js: T) -> Result<Self, Error>

where T: Into<JsValue>, Self: DeserializeOwned,