admin: display on interface time synchronization diff

admin/api/timestamp.go

@@ -0,0 +1,26 @@
+package api
+
+import (
+	"os"
+	"time"
+
+	"github.com/julienschmidt/httprouter"
+)
+
+var TimestampCheck = "submissions"
+
+func init() {
+	router.GET("/api/timestamps.json", apiHandler(
+		func(httprouter.Params, []byte) (interface{}, error) {
+			if stat, err := os.Stat(TimestampCheck); err != nil {
+				return nil, err
+			} else {
+				now := time.Now().UTC()
+				return map[string]interface{}{
+					"frontend": stat.ModTime().UTC(),
+					"backend": now,
+					"diffFB": now.Sub(stat.ModTime()),
+				}, nil
+			}
+		}))
+}