From e2a118cb9910595d4cfdaffa58f5ab3dfd963a7a Mon Sep 17 00:00:00 2001
From: Dominic Dirkx <d.dirkx@tudelft.nl>
Date: Sat, 28 Oct 2023 15:08:11 +0200
Subject: [PATCH] Time conversion modifications/corrections

---
 tests/test_time_conversions.py                | 11 +++++-
 .../expose_astro/expose_time_conversion.cpp   | 38 ++++++++++++++++++-
 2 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/tests/test_time_conversions.py b/tests/test_time_conversions.py
index 1240bb10..17175ab3 100644
--- a/tests/test_time_conversions.py
+++ b/tests/test_time_conversions.py
@@ -1,7 +1,8 @@
 # import sys
 # sys.path.insert(0, "/home/dominic/Tudat/tudat-bundle/tudat-bundle/cmake-build-default/tudatpy")
 
-from datetime import  datetime
+import math
+from datetime import datetime
 from tudatpy.kernel.astro import time_conversion
 
 
@@ -25,4 +26,12 @@ def test_datetime_conversions():
     tudat_datettime = time_conversion.datetime_to_tudat(time_conversion.julian_day_to_calendar_date(julian_day))
     assert julian_day == tudat_datettime.julian_day( )
 
+    pre_1970_date = datetime(1960,1,1,13,7,23,891234)
+    julian_day_to_check = time_conversion.calendar_date_to_julian_day(pre_1970_date)
+
+    assert math.floor( julian_day_to_check ) == 2436935
+    seconds_in_day_to_check = ( julian_day_to_check - math.floor( julian_day_to_check ) ) * 86400.0
+    manual_seconds_in_day = 1 * 3600 + 7 * 60 + 23.891234
+    assert math.fabs( manual_seconds_in_day - seconds_in_day_to_check ) < 1.0E-4
+    print('DATE TIME TEST SUCCESFUL')
 
diff --git a/tudatpy/kernel/expose_astro/expose_time_conversion.cpp b/tudatpy/kernel/expose_astro/expose_time_conversion.cpp
index 1b575fe1..0a7b8b6f 100644
--- a/tudatpy/kernel/expose_astro/expose_time_conversion.cpp
+++ b/tudatpy/kernel/expose_astro/expose_time_conversion.cpp
@@ -41,7 +41,7 @@ tba::DateTime timePointToDateTime(const std::chrono::system_clock::time_point da
 
     using namespace std::chrono;
     microseconds timeInMicroSeconds = duration_cast<microseconds>(datetime.time_since_epoch());
-    auto fractional_seconds = timeInMicroSeconds.count() % 1000000;
+    long long fractional_seconds = timeInMicroSeconds.count() % 1000000LL;
 
     return tba::DateTime( local_tm.tm_year + 1900, local_tm.tm_mon + 1, local_tm.tm_mday,
         local_tm.tm_hour, local_tm.tm_min, static_cast< long double >( local_tm.tm_sec ) +
@@ -91,13 +91,30 @@ namespace tudat
 
 namespace earth_orientation
 {
-std::shared_ptr< TerrestrialTimeScaleConverter >  createDefaultTimeConverterPy( )
+std::shared_ptr<TerrestrialTimeScaleConverter> createDefaultTimeConverterPy( )
 {
     return createDefaultTimeConverter( );
 }
 
 }
 
+namespace basic_astrodynamics
+{
+
+template< typename TimeType >
+DateTime addSecondsToDateTime( const DateTime& dateTime, const TimeType timeToAdd )
+{
+    return getCalendarDateFromTime< Time >( dateTime.epoch< Time >( ) + timeToAdd );
+}
+
+template< typename TimeType >
+DateTime addDaysToDateTime( const DateTime& dateTime, const TimeType daysToAdd )
+{
+    return getCalendarDateFromTime< Time >( dateTime.epoch< Time >( ) + daysToAdd * mathematical_constants::getFloatingInteger< TimeType >( 86400 ) );
+}
+
+}
+
 }
 
 namespace tudatpy {
@@ -122,6 +139,23 @@ void expose_time_conversion(py::module &m) {
           get_docstring("datetime_to_python").c_str()
     );
 
+    m.def("add_seconds_to_datetime",
+          &tba::addSecondsToDateTime< TIME_TYPE >,
+          py::arg("datetime"),
+          py::arg("seconds_to_add"),
+          get_docstring("add_seconds_to_datetime").c_str()
+    );
+
+    m.def("add_days_to_datetime",
+          &tba::addDaysToDateTime< TIME_TYPE >,
+          py::arg("datetime"),
+          py::arg("days_to_add"),
+          get_docstring("add_days_to_datetime").c_str()
+    );
+
+
+
+
 
 
     m.def("calendar_date_to_julian_day",