diff --git a/src/main.sh b/src/main.sh
index 43d4be5..0db0249 100755
--- a/src/main.sh
+++ b/src/main.sh
@@ -1031,6 +1031,7 @@ export COLLECTION_LABELS DAY_START DAY_END AWK_DAYVIEW AWK_WEEKVIEW AWK_PARSE
 # __export()
 # Re-export dynamical variables to subshells.
 __export() {
+  DISPLAY_DATE=$(date -R -d "$DISPLAY_DATE")
   export DISPLAY_DATE WEEKLY_DATA_FILE APPROX_DATA_FILE
   if [ -n "${TZ:-}" ]; then
     export TZ