diff --git a/README.md b/README.md
index 8c431ce..b285f46 100644
--- a/README.md
+++ b/README.md
@@ -142,6 +142,7 @@ Example output with `dirmd -o docs.md ~/repos/myproject --vertical-slices`:
 
 Output is designed for RAG ingestion and LLM context windows, not human presentation:
 
+- **ISO 8601 Timestamp**: Added as a metadata line (`> Generated: ...`) immediately after the H1 header for every new file created.
 - **ASCII tree format** (`+-` instead of Unicode box-drawing) to reduce token overhead
 - **Explicit file delimiters**: `--- FILE: ./path (bytes, lines) ---` and `--- END FILE ---`
 - **Document type markers**: `[ROOT]` and `[SLICE]` in H1 headers
@@ -218,15 +219,17 @@ For full documentation on the Proton Drive CLI, including installation, authenti
 Produces markdown with:
 
 1. Absolute path as H1 header with `[ROOT]` or `[SLICE]` marker
-2. ASCII directory tree (indented with `+-` and `|` characters)
-3. Vertical slices index table (sliced mode only)
-4. All text files with content in fenced code blocks
-5. Explicit `--- FILE: ---` and `--- END FILE ---` delimiters with byte and line counts
-6. Language detection from file extensions
+2. **Timestamp metadata line** (ISO 8601) immediately after the H1 header (only for new files)
+3. ASCII directory tree (indented with `+-` and `|` characters)
+4. Vertical slices index table (sliced mode only)
+5. All text files with content in fenced code blocks
+6. Explicit `--- FILE: ---` and `--- END FILE ---` delimiters with byte and line counts
+7. Language detection from file extensions
 
 Example output structure (non-sliced mode):
 
     # /home/user/repos/myproject [ROOT]
+    > Generated: 2026-09-02T14:30:00Z
 
     ## Directory Tree
 
diff --git a/internal/renderer/renderer.go b/internal/renderer/renderer.go
index 65daa27..c5c2cdb 100644
--- a/internal/renderer/renderer.go
+++ b/internal/renderer/renderer.go
@@ -6,6 +6,7 @@ import (
 	"path/filepath"
 	"sort"
 	"strings"
+	"time"
 	"unicode/utf8"
 
 	"git.flo.fo/FLO/dirmd/internal/tree"
@@ -35,7 +36,12 @@ func Write(result *walker.Result, outputPath string, appendMode bool, singleFile
 		h1Path = filepath.Join(result.AbsRoot, result.Entries[0].RelPath)
 	}
 
-	fmt.Fprintf(&sb, "# %s [ROOT]\n\n", h1Path)
+	fmt.Fprintf(&sb, "# %s [ROOT]\n", h1Path)
+
+	// Add timestamp only if creating a new file (not append mode)
+	if !appendMode {
+		fmt.Fprintf(&sb, "> Generated: %s\n\n", time.Now().Format(time.RFC3339))
+	}
 
 	if !singleFile {
 		root := tree.Build(result.Entries)
@@ -162,7 +168,9 @@ func writeRootSlice(path, absRoot, rootName, repoName string, rootFiles []walker
 
 	var sb strings.Builder
 
-	fmt.Fprintf(&sb, "# %s [ROOT]\n\n", absRoot)
+	fmt.Fprintf(&sb, "# %s [ROOT]\n", absRoot)
+	// Timestamp for new file creation
+	fmt.Fprintf(&sb, "> Generated: %s\n\n", time.Now().Format(time.RFC3339))
 
 	treeLines := buildTreeWithRefs(rootName, repoName, topLevelDirs, rootFiles)
 	sb.WriteString("## Directory Tree\n\n")
@@ -239,7 +247,9 @@ func writeDirSlice(path, absDir, absRoot, dirName string, treeEntries, fileEntri
 
 	var sb strings.Builder
 
-	fmt.Fprintf(&sb, "# %s [SLICE]\n\n", absDir)
+	fmt.Fprintf(&sb, "# %s [SLICE]\n", absDir)
+	// Timestamp for new file creation
+	fmt.Fprintf(&sb, "> Generated: %s\n\n", time.Now().Format(time.RFC3339))
 	fmt.Fprintf(&sb, "Root document: %s\n\n", rootFileName)
 
 	sb.WriteString("## Directory Tree\n\n")