diff --git a/arrange.go b/arrange.go
index aba4f60..4d4059f 100644
--- a/arrange.go
+++ b/arrange.go
@@ -13,6 +13,23 @@ import (
 	"time"
 )
 
+var exts map[string]bool
+
+func init() {
+	exts = map[string]bool{
+		// images
+		".jpg":  true,
+		".jpeg": true,
+		".png":  true,
+		".gif":  true,
+
+		// videos
+		".mov": true,
+		".mp4": true,
+		".m4v": true,
+	}
+}
+
 type File interface {
 	Move(root string) error
 }
@@ -30,7 +47,7 @@ func PrepOutput(root string) error {
 	return nil
 }
 
-func Source(root string, exts map[string]bool) <-chan string {
+func Source(root string) <-chan string {
 	out := make(chan string)
 	go func() {
 		err := filepath.Walk(
@@ -42,8 +59,6 @@ func Source(root string, exts map[string]bool) <-chan string {
 				ext := strings.ToLower(filepath.Ext(path))
 				if _, ok := exts[ext]; ok {
 					out <- path
-				} else {
-					log.Printf("ignoring: %q", path)
 				}
 				return nil
 			},
@@ -118,7 +133,6 @@ func _parse(path string) (File, error) {
 				success = true
 			}
 			if !success {
-				log.Printf("no exif for %q: %+v", path, err)
 				t, err = mtime(path)
 			}
 			if err != nil {
@@ -134,11 +148,9 @@ func _parse(path string) (File, error) {
 			return nil, fmt.Errorf("problem calculating checksum on %q: %v", path, err)
 		}
 		r = Image{
-			Path:  path,
-			Hash:  fmt.Sprintf("%x", hash.Sum(nil)),
-			Year:  fmt.Sprintf("%04d", t.Year()),
-			Month: fmt.Sprintf("%02d", t.Month()),
-			Time:  fmt.Sprintf("%d", t.UnixNano()),
+			Path: path,
+			Hash: fmt.Sprintf("%x", hash.Sum(nil)),
+			Time: t,
 		}
 	case ".png":
 		return nil, fmt.Errorf("NYI: %q", path)
diff --git a/cmd/am/main.go b/cmd/am/main.go
index 4a3805b..fe2c5fc 100644
--- a/cmd/am/main.go
+++ b/cmd/am/main.go
@@ -1,9 +1,11 @@
 package main
 
 import (
+	"flag"
 	"fmt"
 	"log"
 	"os"
+	"runtime"
 
 	"mcquay.me/arrange"
 )
@@ -16,36 +18,31 @@ type stats struct {
 	moved int
 }
 
+var cores = flag.Int("cores", 0, "how many threads to use")
+
 func main() {
+	flag.Parse()
 	log.SetFlags(log.Lshortfile)
-	if len(os.Args) != 3 {
+	if len(flag.Args()) != 2 {
 		fmt.Fprintf(os.Stderr, "%s\n", usage)
 		os.Exit(1)
 	}
-	in, out := os.Args[1], os.Args[2]
+	in, out := flag.Args()[0], flag.Args()[1]
 
 	if err := arrange.PrepOutput(out); err != nil {
 		fmt.Fprintf(os.Stderr, "problem creating directory structure: %v", err)
 		os.Exit(1)
 	}
 
-	exts := map[string]bool{
-		// images
-		".jpg":  true,
-		".jpeg": true,
-		".png":  true,
-		".gif":  true,
-
-		// videos
-		".mov": true,
-		".mp4": true,
-		".m4v": true,
-	}
-
-	work := arrange.Source(in, exts)
+	work := arrange.Source(in)
 	streams := []<-chan arrange.File{}
 
-	for w := 0; w < 16; w++ {
+	workers := runtime.NumCPU()
+	if *cores != 0 {
+		workers = *cores
+	}
+
+	for w := 0; w < workers; w++ {
 		streams = append(streams, arrange.Parse(work))
 	}
 
diff --git a/image.go b/image.go
index 968dc39..77f98e6 100644
--- a/image.go
+++ b/image.go
@@ -20,11 +20,9 @@ func (m Media) Move(root string) error {
 }
 
 type Image struct {
-	Path  string
-	Hash  string
-	Year  string
-	Month string
-	Time  string
+	Path string
+	Hash string
+	Time time.Time
 }
 
 func (im Image) Move(root string) error {
@@ -49,11 +47,16 @@ func (im Image) Move(root string) error {
 	if _, err := io.Copy(out, f); err != nil {
 		return fmt.Errorf("trouble copying file: %v", err)
 	}
-	if err := os.MkdirAll(filepath.Join(root, "date", im.Year, im.Month), 0755); err != nil {
+
+	year := fmt.Sprintf("%04d", im.Time.Year())
+	month := fmt.Sprintf("%02d", im.Time.Month())
+	ts := fmt.Sprintf("%d", im.Time.UnixNano())
+
+	if err := os.MkdirAll(filepath.Join(root, "date", year, month), 0755); err != nil {
 		return fmt.Errorf("problem creating date directory: %v", err)
 	}
 
-	date := filepath.Join(root, "date", im.Year, im.Month, im.Time)
+	date := filepath.Join(root, "date", year, month, ts)
 	name := date + ".jpg"
 	for i := 0; i < 10000; i++ {
 		if _, err := os.Stat(name); os.IsNotExist(err) {