diff --git a/src/index.js b/src/index.js
index 29adf1d4..799bb3a3 100644
--- a/src/index.js
+++ b/src/index.js
@@ -401,5 +401,5 @@ dayjs.unix = timestamp => (
 
 dayjs.en = Ls[L]
 dayjs.Ls = Ls
-
+dayjs.p = {}
 export default dayjs
diff --git a/src/plugin/customParseFormat/index.js b/src/plugin/customParseFormat/index.js
index c1c7b85b..d96df6fe 100644
--- a/src/plugin/customParseFormat/index.js
+++ b/src/plugin/customParseFormat/index.js
@@ -182,6 +182,7 @@ const parseFormattedInput = (input, format, utc) => {
 
 
 export default (o, C, d) => {
+  d.p.customParseFormat = true
   const proto = C.prototype
   const oldParse = proto.parse
   proto.parse = function (cfg) {
diff --git a/src/plugin/devHelper/index.js b/src/plugin/devHelper/index.js
new file mode 100644
index 00000000..40e1f38a
--- /dev/null
+++ b/src/plugin/devHelper/index.js
@@ -0,0 +1,18 @@
+/* eslint-disable no-console */
+export default (o, c, d) => {
+  if (process.env.NODE_ENV !== 'production') {
+    const proto = c.prototype
+    const oldParse = proto.parse
+    proto.parse = function (cfg) {
+      const { date } = cfg
+      if (typeof date === 'string' && date.length === 13) {
+        console.warn(`To parse a Unix timestamp like ${date}, you should pass it as a Number. https://day.js.org/docs/en/parse/unix-timestamp-milliseconds`)
+      }
+      if (cfg.args.length >= 2 && !d.p.customParseFormat) {
+        console.warn(`To parse a date-time string like ${date} using the given format, you should enable customParseFormat plugin first. https://day.js.org/docs/en/parse/string-format`)
+      }
+      return oldParse.bind(this)(cfg)
+    }
+  }
+}
+
diff --git a/types/plugin/devHelper.d.ts b/types/plugin/devHelper.d.ts
new file mode 100644
index 00000000..30ec75e5
--- /dev/null
+++ b/types/plugin/devHelper.d.ts
@@ -0,0 +1,4 @@
+import { PluginFunc } from 'dayjs'
+
+declare const plugin: PluginFunc
+export = plugin