diff --git a/dayjs_format_ms.coffee b/dayjs_format_ms.coffee
deleted file mode 100644
index 58995fe..0000000
--- a/dayjs_format_ms.coffee
+++ /dev/null
@@ -1,16 +0,0 @@
-module.exports = (o, c, d) ->
-  proto = c.prototype
-  old_format = proto.format
-  proto.format = (fmt_str = 'YYYY-MM-DDTHH:mm:ssZ') ->
-    locale = @$locale()
-    utils = @$utils()
-    r = fmt_str.replace /\[([^\]]+)]|SSS|S{2,2}|S/g, (word) =>
-      switch word
-        when 'S'
-          "#{@$ms}"
-        when 'SS'
-          ms = Math.round(@$ms / 10)
-          "#{ms}".padStart(2, '0')
-        else
-          word
-    old_format.bind(this) r