tempoch-cpp API Documentation

tempoch-cpp is a modern, header-only C++17 library for astronomical time primitives. It wraps the Rust-based tempoch through its C FFI layer (tempoch-ffi), exposing the same two-axis model as Rust: physical scale and external format are separate type parameters.

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Features

Feature	Description
**CivilTime**	Civil UTC date-time struct (year/month/day/hour/min/sec) with nanosecond precision
**Time<scale::S>**	Canonical instant on a physical timescale, stored as split J2000 seconds
**EncodedTime<S, F>**	Typed external encoding such as JulianDate<scale::TT> or ModifiedJulianDate<scale::UTC>
**TimeContext**	Explicit context for UT1 and historical UTC routes
**Period<T>**	Half-open [start, end) interval over any supported time representation
Exception hierarchy	All FFI status codes map to typed C++ exceptions
Header-only	Drop into any project — no separate compilation step

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Quick Start

#include <tempoch/tempoch.hpp>
#include <tempoch/formats/jd.hpp>
#include <tempoch/formats/mjd.hpp>
#include <tempoch/scales/utc.hpp>
#include <iostream>
 
int main() {
    using namespace tempoch;
 
    CivilTime civil{2026, 7, 15, 22, 0, 0};
    auto jd_tt = JulianDate<scale::TT>::from_utc(civil);
    auto mjd_tt = ModifiedJulianDate<scale::TT>::from_jd(jd_tt);
    auto utc = Time<scale::TT>::from_encoded(jd_tt).to<scale::UTC>();
    auto jd_utc = utc.to<format::JD>();
 
    std::cout << "Civil UTC : " << civil << "\n";
    std::cout << "JD(TT)    : " << jd_tt << "\n";
    std::cout << "JD(UTC)   : " << jd_utc << "\n";
    std::cout << "MJD(TT)   : " << mjd_tt << "\n";
}

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Architecture

┌──────────────┐
│  C++ user    │   #include <tempoch/tempoch.hpp>
│  code        │
└──────┬───────┘
       │  header-only (inline)
┌──────▼───────┐
│ tempoch-cpp  │   C++17 value types: CivilTime, Time<S>, EncodedTime<S,F>, Period<T>
│  (headers)   │
└──────┬───────┘
       │  extern "C" calls
┌──────▼───────┐
│ tempoch-ffi  │   C ABI (cbindgen-generated from Rust)
│ (.so/.dylib) │
└──────┬───────┘
       │
┌──────▼─────────┐
│ tempoch (Rust) │   Time arithmetic, calendar conversion, period algebra
└────────────────┘

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Modules

• tempoch/tempoch.hpp — umbrella include for the full public API
• tempoch/scales/scales.hpp — scale tag index header
• tempoch/formats/formats.hpp — format tag index header
• tempoch/time.hpp — CivilTime, TT-default JulianDate / MJD, explicit Time<scale::S>, and TimeContext
• tempoch/period.hpp — Period interval type
• tempoch/ffi_core.hpp — FFI helpers and exception hierarchy

Migration Notes

• Default astronomy-facing code should use TT-based JulianDate, MJD, and Period.
• Civil construction is available directly through JulianDate<scale::TT>::from_utc(...) and ModifiedJulianDate<scale::TT>::from_utc(...).
• The explicit typed core remains available through Time<scale::S> and EncodedTime<S, F> for mixed-scale work.

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Error Model

FFI tempoch_status_t codes are translated into typed C++ exceptions:

Exception	When thrown
TempochException	Base class for all tempoch errors
NullPointerError	FFI returned a null handle
UtcConversionError	Invalid or out-of-range calendar fields
InvalidPeriodError	start > end or malformed period
NoIntersectionError	Period intersection on non-overlapping intervals

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Prerequisites

• C++17 compiler (GCC 8+, Clang 7+, MSVC 2019+)
• CMake 3.15+
• Rust toolchain (cargo) — tempoch-ffi is built automatically

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Building

git clone --recurse-submodules <url>
cd tempoch-cpp
 
cmake -S . -B build
cmake --build build --parallel
ctest --test-dir build --output-on-failure
 
./build/01_quickstart

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Building This Documentation

cmake -S . -B build -G Ninja -DTEMPOCH_BUILD_DOCS=ON
cmake --build build --target docs

Then open:

• build/docs/doxygen/html/index.html