Reporter: More chrono conversions

Author: Joseph-Edwards

src/runner.cpp

@@ -32,6 +32,23 @@
 namespace libsemigroups {
   namespace py = pybind11;
 
+  namespace {
+    std::chrono::system_clock::time_point
+    to_system(std::chrono::high_resolution_clock::time_point tp) {
+      using namespace std::chrono;
+      if constexpr (std::is_same_v<system_clock, high_resolution_clock>) {
+        return tp;
+      } else {
+        // Account for the difference between system_clock and
+        // high_resolution_clock
+        auto sys_now      = system_clock::now();
+        auto high_res_now = high_resolution_clock::now();
+        return time_point_cast<system_clock::duration>(tp - high_res_now
+                                                       + sys_now);
+      }
+    }
+  }  // namespace
+
   void init_reporter(py::module& m) {
     m.def(
         "delta",
@@ -193,9 +210,7 @@ Get the minimum elapsed time between reports.
 )pbdoc");
     thing.def(
         "start_time",
-        [](Reporter const& self) -> std::chrono::system_clock::time_point {
-          return self.start_time();
-        },
+        [](Reporter const& self) { return to_system(self.start_time()); },
         R"pbdoc(
 Get the start time.
 
@@ -250,7 +265,7 @@ Reset the start time (and last report) to now.
                warn(message, DeprecationWarning, level)
             )");
 
-          return self.last_report();
+          return to_system(self.last_report());
         },
         R"pbdoc(
 Get the time point of the last report. This function returns the time point of the