From 2de9c39f7ac5663fabcc38d19e0ef1f57f229b9c Mon Sep 17 00:00:00 2001
From: Iskren Chernev <iskren.chernev@gmail.com>
Date: Sat, 19 Sep 2015 18:41:10 -0700
Subject: [PATCH] get,set,add,subtract handle properly invalid moments

---
 src/lib/moment/add-subtract.js | 6 ++++++
 src/lib/moment/get-set.js      | 7 +++++--
 src/lib/units/month.js         | 5 +++++
 3 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/src/lib/moment/add-subtract.js b/src/lib/moment/add-subtract.js
index ebfe674b2..988eff321 100644
--- a/src/lib/moment/add-subtract.js
+++ b/src/lib/moment/add-subtract.js
@@ -25,6 +25,12 @@ export function addSubtract (mom, duration, isAdding, updateOffset) {
     var milliseconds = duration._milliseconds,
         days = duration._days,
         months = duration._months;
+
+    if (!mom.isValid()) {
+        // No op
+        return;
+    }
+
     updateOffset = updateOffset == null ? true : updateOffset;
 
     if (milliseconds) {
diff --git a/src/lib/moment/get-set.js b/src/lib/moment/get-set.js
index 0f2be6045..a8c6ef691 100644
--- a/src/lib/moment/get-set.js
+++ b/src/lib/moment/get-set.js
@@ -14,11 +14,14 @@ export function makeGetSet (unit, keepTime) {
 }
 
 export function get (mom, unit) {
-    return mom._d['get' + (mom._isUTC ? 'UTC' : '') + unit]();
+    return mom.isValid() ?
+        mom._d['get' + (mom._isUTC ? 'UTC' : '') + unit]() : NaN;
 }
 
 export function set (mom, unit, value) {
-    return mom._d['set' + (mom._isUTC ? 'UTC' : '') + unit](value);
+    if (mom.isValid()) {
+        mom._d['set' + (mom._isUTC ? 'UTC' : '') + unit](value);
+    }
 }
 
 // MOMENTS
diff --git a/src/lib/units/month.js b/src/lib/units/month.js
index 63d18b47f..39193e700 100644
--- a/src/lib/units/month.js
+++ b/src/lib/units/month.js
@@ -100,6 +100,11 @@ export function localeMonthsParse (monthName, format, strict) {
 export function setMonth (mom, value) {
     var dayOfMonth;
 
+    if (!mom.isValid()) {
+        // No op
+        return mom;
+    }
+
     // TODO: Move this out of here!
     if (typeof value === 'string') {
         value = mom.localeData().monthsParse(value);
-- 
2.47.2