diff --git a/src/harmony/app/canvas.cpy b/src/harmony/app/canvas.cpy
index d27aa27..93f0e12 100644
--- a/src/harmony/app/canvas.cpy
+++ b/src/harmony/app/canvas.cpy
@@ -117,7 +117,7 @@ namespace app_ui:
 
     void sanitize_filename(string &name):
       for i := 0; i < name.length(); i++:
-        if name[i] == '/':
+        if name[i] == '/' or name[i] == ':':
           name[i] = '_'
 
     auto get_stroke_width():
@@ -363,7 +363,7 @@ namespace app_ui:
       self.mark_redraw()
 
 
-    // we tack on ".hrm" to the filename
+    // we tack on ".[timestamp].hrm" to the filename
     void save_project(bool overwrite=false):
       sanitize_filename(self.project_name)
       debug "SAVING PROJECT", self.project_name
diff --git a/src/rmkit/fb/fb.cpy b/src/rmkit/fb/fb.cpy
index e7a28b9..e148f6a 100644
--- a/src/rmkit/fb/fb.cpy
+++ b/src/rmkit/fb/fb.cpy
@@ -418,7 +418,7 @@ namespace framebuffer:
       time (&rawtime);
       timeinfo = localtime(&rawtime);
 
-      strftime(buffer,sizeof(buffer),"%Y-%m-%d-%H:%M:%S",timeinfo);
+      strftime(buffer,sizeof(buffer),"%Y-%m-%d-%H_%M_%S",timeinfo);
       std::string str(buffer);
 
       return str