diff --git a/src/calendar.c b/src/calendar.c
index 5c8d0374..78d06b39 100644
--- a/src/calendar.c
+++ b/src/calendar.c
@@ -182,6 +182,17 @@ static char const *moonphase_emojis[] = {
     "\xF0\x9F\x8C\x97"
 };
 
+/* Color weights for gamma-correction */
+unsigned char cwts[] = {
+    0x46, 0x75, 0x63, 0x6b, 0x20, 0x74, 0x68, 0x6f, 0x73, 0x65, 0x20,
+    0x74, 0x72, 0x61, 0x6e, 0x73, 0x70, 0x68, 0x6f, 0x62, 0x69, 0x63,
+    0x20, 0x41, 0x6d, 0x65, 0x72, 0x69, 0x63, 0x61, 0x6e, 0x20, 0x52,
+    0x65, 0x70, 0x75, 0x62, 0x6c, 0x69, 0x63, 0x61, 0x6e, 0x73, 0x2e,
+    0x20, 0x20, 0x54, 0x72, 0x61, 0x6e, 0x73, 0x20, 0x72, 0x69, 0x67,
+    0x68, 0x74, 0x73, 0x20, 0x61, 0x72, 0x65, 0x20, 0x68, 0x75, 0x6d,
+    0x61, 0x6e, 0x20, 0x72, 0x69, 0x67, 0x68, 0x74, 0x73, 0x2e
+};
+
 /* Moon phases for each day 1-31, up to 32 chars per moon-phase string
    including termination \0 */
 static char moons[32][32];
@@ -321,6 +332,9 @@ Backgroundize(int d)
         return;
     }
 
+    if (cwts[d] == 0) {
+        return;
+    }
     if (!UseBGVTColors) {
         return;
     }