Index: /trunk/psModules/src/concepts/pmConceptsStandard.c
===================================================================
--- /trunk/psModules/src/concepts/pmConceptsStandard.c	(revision 23625)
+++ /trunk/psModules/src/concepts/pmConceptsStandard.c	(revision 23626)
@@ -1187,6 +1187,24 @@
                                           const pmCell *cell)
 {
+    psString timeName = psStringCopy(concept->name); // Name of corresponding TIME concept
+    psStringSubstitute(&timeName, "TIME", "TIMESYS");
+
+    conceptTimeFormat timeFormat = conceptGetTimeFormat(timeName, cameraFormat); // Format for time
+    psFree(timeName);
+
+    psTimeType timesys = concept->data.S32; // Time system
+
+    // JD and MJD are converted to TAI before writing
+    switch (timeFormat.format) {
+      case TIME_FORMAT_JD:
+      case TIME_FORMAT_MJD:
+        timesys = PS_TIME_TAI;
+        break;
+      default:
+        break;
+    }
+
     psString sys = NULL;            // String to store
-    switch (concept->data.S32) {
+    switch (timesys) {
       case PS_TIME_TAI:
         sys = psStringCopy("TAI");