examples

.gitignore

@@ -1,6 +1,7 @@
 # Artifacts
 build*/
 coverage*/
+coverage.xml
 
 # Prerequisites
 *.d

CMakeLists.txt

@@ -121,7 +121,7 @@ FetchContent_MakeAvailable(googletest)
 # Enable testing
 enable_testing()
 
-# Example
+# Examples
 add_executable(time_example examples/time_example.cpp)
 target_link_libraries(time_example PRIVATE tempoch_cpp)
 if(DEFINED _tempoch_rpath)
@@ -131,6 +131,16 @@ if(DEFINED _tempoch_rpath)
     )
 endif()
 
+# All time-scale types: JD, MJD, TDB, TT, TAI, TCG, TCB, GPS, UT, JDE, UnixTime
+add_executable(timescales examples/timescales.cpp)
+target_link_libraries(timescales PRIVATE tempoch_cpp)
+if(DEFINED _tempoch_rpath)
+    set_target_properties(timescales PROPERTIES
+        BUILD_RPATH ${_tempoch_rpath}
+        INSTALL_RPATH ${_tempoch_rpath}
+    )
+endif()
+
 # Test executables with Google Test
 set(TEST_SOURCES
     tests/main.cpp

examples/timescales.cpp

@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+// Copyright (C) 2026 Vallés Puig, Ramon
+
+/**
+ * @file timescales.cpp
+ * @example timescales.cpp
+ * @brief Demonstrates every tempoch time-scale type and cross-scale conversion.
+ *
+ * Build and run:
+ *   cmake -B build && cmake --build build
+ *   ./build/timescales
+ *
+ * Time scales shown:
+ *   JulianDate (JD), MJD, TDB, TT, TAI, TCG, TCB, GPS, UT (UT1),
+ *   JDE (Julian Ephemeris Date ≡ TDB), UnixTime
+ */
+
+#include <cmath>
+#include <iomanip>
+#include <iostream>
+#include <tempoch/tempoch.hpp>
+
+int main() {
+  using namespace tempoch;
+
+  std::cout << "=== tempoch Time-Scale Showcase ===\n\n";
+
+  // ── 1. Reference epoch J2000.0 ─────────────────────────────────────────
+  //
+  // JD 2 451 545.0 = 2000-01-01T12:00:00 TT.
+  // (2000-01-01T11:58:56Z in UTC because ΔT ≈ 63.8 s at this epoch.)
+  JulianDate jd = JulianDate(2'451'545.0);
+  std::cout << "Reference: J2000.0\n";
+  std::cout << "  JD value: " << std::fixed << std::setprecision(6)
+            << jd.value() << "\n\n";
+
+  // ── 2. Convert to every scale ───────────────────────────────────────────
+  MJD mjd = jd.to<MJDScale>();
+  JDE jde = jd.to<JDEScale>();
+  TT tt = jd.to<TTScale>();
+  TAI tai = jd.to<TAIScale>();
+  TDB tdb = jd.to<TDBScale>();
+  TCG tcg = jd.to<TCGScale>();
+  TCB tcb = jd.to<TCBScale>();
+  GPS gps = jd.to<GPSScale>();
+  UT ut = jd.to<UTScale>();
+  UnixTime ux = jd.to<UnixTimeScale>();
+
+  std::cout << "Scale conversions at J2000.0:\n";
+  std::cout << std::fixed << std::setprecision(9);
+  std::cout << "  JD   (JD 2451545.0)            : " << jd.value() << "\n";
+  std::cout << "  MJD  (JD − 2400000.5)          : " << mjd.value() << "\n";
+  std::cout << "  JDE  (≡ TDB, as JD)            : " << jde.value() << "\n";
+  std::cout << "  TT   (TAI + 32.184 s)          : " << tt.value() << "\n";
+  std::cout << "  TAI  (TT  − 32.184 s)          : " << tai.value() << "\n";
+  std::cout << "  TDB  (≈ TT, periodic correction): " << tdb.value() << "\n";
+  std::cout << "  TCG  (TT + secular rate)       : " << tcg.value() << "\n";
+  std::cout << "  TCB  (TDB + secular rate)      : " << tcb.value() << "\n";
+  std::cout << "  GPS  (TAI − 19 s)              : " << gps.value() << "\n";
+  std::cout << "  UT1  (UTC + ΔT_earth)          : " << ut.value() << "\n";
+  std::cout << std::scientific << std::setprecision(3);
+  std::cout << "  Unix (seconds since 1970-01-01): " << ux.value() << "\n\n";
+
+  // ── 3. Fixed offsets between scales (seconds) ──────────────────────────
+  constexpr double SECS_PER_DAY = 86'400.0;
+  double tt_tai_s = (tt.value() - tai.value()) * SECS_PER_DAY;
+  double tai_gps_s = (tai.value() - gps.value()) * SECS_PER_DAY;
+
+  std::cout << std::fixed << std::setprecision(3);
+  std::cout << "Fixed offsets between scales:\n";
+  std::cout << "  TT − TAI  = " << tt_tai_s << " s  (constant 32.184 s)\n";
+  std::cout << "  TAI − GPS = " << tai_gps_s
+            << " s  (constant 19 s since 1980)\n\n";
+
+  // ── 4. Round-trips ──────────────────────────────────────────────────────
+  JulianDate jd_from_mjd = mjd.to<JDScale>();
+  JulianDate jd_from_tt = tt.to<JDScale>();
+  JulianDate jd_from_tai = tai.to<JDScale>();
+  JulianDate jd_from_tdb = tdb.to<JDScale>();
+
+  std::cout << std::scientific << std::setprecision(3);
+  std::cout << "Round-trip JD → X → JD residuals (days):\n";
+  std::cout << "  JD → MJD → JD : "
+            << std::abs(jd_from_mjd.value() - jd.value()) << "\n";
+  std::cout << "  JD → TT  → JD : " << std::abs(jd_from_tt.value() - jd.value())
+            << "\n";
+  std::cout << "  JD → TAI → JD : "
+            << std::abs(jd_from_tai.value() - jd.value()) << "\n";
+  std::cout << "  JD → TDB → JD : "
+            << std::abs(jd_from_tdb.value() - jd.value()) << "\n\n";
+
+  // ── 5. Observable epoch (civil time → all scales) ──────────────────────
+  UTC obs(2026, 7, 15, 22, 0, 0);
+  JulianDate jd_obs = JulianDate::from_utc(obs);
+  MJD mjd_obs = jd_obs.to<MJDScale>();
+  TT tt_obs = jd_obs.to<TTScale>();
+  TAI tai_obs = jd_obs.to<TAIScale>();
+  TDB tdb_obs = jd_obs.to<TDBScale>();
+
+  std::cout << std::fixed << std::setprecision(6);
+  std::cout << "Observation: 2026-07-15 22:00:00 UTC\n";
+  std::cout << "  JD   : " << jd_obs.value() << "\n";
+  std::cout << "  MJD  : " << mjd_obs.value() << "\n";
+  std::cout << "  TT   : " << tt_obs.value() << "\n";
+  std::cout << "  TAI  : " << tai_obs.value() << "\n";
+  std::cout << "  TDB  : " << tdb_obs.value() << "\n";
+  std::cout << "  Julian centuries since J2000: " << jd_obs.julian_centuries()
+            << "\n\n";
+
+  // ── 6. Cross-scale arithmetic: add 1 hour in GPS, round-trip to JD ─────
+  constexpr double ONE_HOUR_DAYS = 1.0 / 24.0;
+  GPS gps_obs = jd_obs.to<GPSScale>();
+  GPS gps_obs_plus1h(gps_obs.value() + ONE_HOUR_DAYS);
+  JulianDate jd_plus1h = gps_obs_plus1h.to<JDScale>();
+
+  std::cout << "GPS +1 h → JD difference: " << std::fixed
+            << std::setprecision(6)
+            << (jd_plus1h.value() - jd_obs.value()) * 24.0 << " h\n";
+
+  std::cout << "\n=== All time-scale examples completed successfully ===\n";
+  return 0;
+}