Index: trunk/FACT++/src/moon.cc
===================================================================
--- trunk/FACT++/src/moon.cc	(revision 18466)
+++ trunk/FACT++/src/moon.cc	(revision 18467)
@@ -183,4 +183,10 @@
     cout << 90-hrz.alt   << '\n';
 
+    const double   kSynMonth = 29.53058868; // synodic month (new Moon to new Moon)
+    const double   kEpoch0   = 44240.37917; // First full moon after 1980/1/1
+    const double   kInstall  = 393;         // Moon period if FACT installation
+    const uint32_t period    = floor(((time.Mjd()-kEpoch0)/kSynMonth-kInstall));
+
+    cout << period       << '\n';
     cout << moon.visible << '\n';
     cout << moon.disk    << '\n';