Index: trunk/ippTools/src/dettoolConfig.c
===================================================================
--- trunk/ippTools/src/dettoolConfig.c	(revision 31375)
+++ trunk/ippTools/src/dettoolConfig.c	(revision 31383)
@@ -103,5 +103,6 @@
     psMetadataAddF64(definebyqueryArgs, PS_LIST_TAIL, "-sun_angle_max",  0,            "define max solar angle", NAN);
     psMetadataAddTime(definebyqueryArgs, PS_LIST_TAIL, "-registered",  0,            "time detrend run was registered", now);
-    psMetadataAddTime(definebyqueryArgs, PS_LIST_TAIL, "-time_begin",  0,            "detrend applies to exposures taken during this period", NULL);
+    psMetadataAddTime(definebyqueryArgs, PS_LIST_TAIL, "-time_begin",  0,            "detrend applies to exposures taken during this period (required)", NULL);
+    // i'm requiring time_begin because otherwise if not specified detselect will pick the wrong detrend for old date ranges (it will pick the most recent one with NULL)
     psMetadataAddTime(definebyqueryArgs, PS_LIST_TAIL, "-time_end",  0,            "detrend applies to exposures taken during this period", NULL);
     psMetadataAddTime(definebyqueryArgs, PS_LIST_TAIL, "-use_begin",  0,            "start of detrend run applicable period", NULL);