diff --git a/add_timestamp.sh b/add_timestamp.sh
new file mode 100755
index 00000000..8ba00975
--- /dev/null
+++ b/add_timestamp.sh
@@ -0,0 +1,29 @@
+#!/bin/bash
+#別のマシンで作ったファイルはわからんので、それぞれのでやって古い方で上書きする必要がある
+cwd=`dirname "${0}"`
+FILES=$(find $cwd/content -name "*.md")
+IFS=$'\n'
+for f in $FILES
+do
+BDATE=$(stat -f "%SB" "$f");
+FLINE=$(head -n 1 "$f");
+if [[ "$FLINE" == "---" ]];
+then
+echo "$f has frontmatter";
+ORIGINDATE=$(yq --front-matter=extract '.date' "$f" | date "+%s")
+LOCALDATE=$(LC_ALL=C date -j -f "%b %d %H:%M:%S %Y" "$BDATE" | date "+%s");
+
+if [ $LOCALDATE -lt $ORIGINDATE ]; then # -lt : '<'
+    echo "date of local file is older. overwriting."
+    DATE=$(LC_ALL=C date -j -Iseconds -f "%b %d %H:%M:%S %Y" "$BDATE");
+    echo "$f : $DATE"
+    echo $DATE | xargs -I{} yq -i --front-matter="process" '.date="{}"' "$f"
+fi
+else
+echo "$f has no frontmatter, adding";
+gsed -i '1i---\n---' "$f"
+DATE=$(LC_ALL=C date -j -Iseconds -f "%b %d %H:%M:%S %Y" "$BDATE");
+echo "$f : $DATE"
+echo $DATE | xargs -I{} yq -i --front-matter="process" '.date="{}"' "$f"
+fi
+done
\ No newline at end of file