tempoch-cpp

tempoch-cpp is a C++17 library for astronomical time primitives. It provides a header-only C++ API backed by the Rust tempoch-ffi engine (via a C FFI), with typed time scales, UTC conversions, and period operations.

Features

• Strongly typed time values such as JulianDate, MJD, UTC, TT, TAI, TDB, TCG, TCB, GPS, UT, JDE, and UnixTime
• Civil UTC representation with nanosecond precision via tempoch::CivilTime
• Cross-scale conversion helpers such as from_utc(), to_utc(), to_jd(), and to_mjd()
• Time arithmetic using qtty-cpp duration quantities such as qtty::Day, qtty::Hour, and qtty::Minute
• Period<T> intervals with typed start/end access, intersection, and duration conversion
• CMake target (tempoch_cpp) for straightforward integration

Requirements

• CMake 3.15+
• C++17 compiler (GCC 8+, Clang 7+, MSVC 2019+)
• Rust/Cargo (builds tempoch-ffi)

Build and Test

git clone --recurse-submodules <repo-url>
cd tempoch-cpp

cmake -S . -B build
cmake --build build --parallel
ctest --test-dir build --output-on-failure
./build/time_example

If you cloned without submodules:

git submodule update --init --recursive

Usage

#include <iostream>
#include <qtty/qtty.hpp>
#include <tempoch/tempoch.hpp>

using namespace tempoch;

int main() {
    UTC utc(2026, 7, 15, 22, 0, 0);

    auto jd = JulianDate::from_utc(utc);
    auto mjd = MJD::from_jd(jd);

    std::cout << "UTC: " << utc << "\n";
    std::cout << "JD:  " << jd << "\n";
    std::cout << "MJD: " << mjd << "\n";

    Period observing_window(MJD(60200.0), MJD(60200.5));
    std::cout << "Duration: "
              << observing_window.duration<qtty::Hour>()
              << "\n";
}

Durations and Arithmetic

Time arithmetic uses qtty-cpp quantities. Subtracting two times returns a typed duration, and adding or subtracting a quantity shifts the time value.

auto jd0 = JulianDate::J2000();
auto jd1 = jd0 + qtty::Hour(12.0);
auto dt = jd1 - jd0;

std::cout << dt.to<qtty::Hour>() << "\n";

Documentation

• docs/mainpage.md (API overview)
• examples/time_example.cpp (basic usage)
• include/tempoch/tempoch.hpp (umbrella public header)

Integration

Add as a Subdirectory

add_subdirectory(path/to/tempoch-cpp)
target_link_libraries(your_target PRIVATE tempoch_cpp)

Install and Use find_package

cmake --install build

find_package(tempoch_cpp REQUIRED)
target_link_libraries(your_target PRIVATE tempoch::tempoch_cpp)

License

This repository wraps the upstream tempoch project (git submodule in tempoch/). See tempoch/LICENSE for licensing details.