diff --git a/app/Models/Invoice.php b/app/Models/Invoice.php
index 2065f80e00be..d2124dad42c8 100644
--- a/app/Models/Invoice.php
+++ b/app/Models/Invoice.php
@@ -14,6 +14,7 @@ use DateTime;
 use Illuminate\Database\Eloquent\SoftDeletes;
 use Laracasts\Presenter\PresentableTrait;
 use Utils;
+use Carbon;
 
 /**
  * Class Invoice.
@@ -1159,28 +1160,24 @@ class Invoice extends EntityModel implements BalanceAffecting
             return false;
         }
 
-        if (! $this->start_date || strtotime($this->start_date) > strtotime('now')) {
+        $account = $this->account;
+        $timezone = $account->getTimezone();
+
+        if (! $this->start_date || Carbon::parse($this->start_date, $timezone)->isFuture()) {
             return false;
         }
 
-        if ($this->end_date && strtotime($this->end_date) < strtotime('now')) {
+        if ($this->end_date && Carbon::parse($this->end_date, $timezone)->isPast()) {
             return false;
         }
 
-        $dayOfWeekToday = date('w');
-        $dayOfWeekStart = date('w', strtotime($this->start_date));
-
-        $dayOfMonthToday = date('j');
-        $dayOfMonthStart = date('j', strtotime($this->start_date));
-
         if (! $this->last_sent_date) {
             return true;
         } else {
-            $date1 = new DateTime($this->last_sent_date);
-            $date2 = new DateTime();
-            $diff = $date2->diff($date1);
-            $daysSinceLastSent = $diff->format('%a');
-            $monthsSinceLastSent = ($diff->format('%y') * 12) + $diff->format('%m');
+            $date1 = Carbon::parse($this->last_sent_date, $timezone);
+            $date2 = Carbon::now($timezone);
+            $daysSinceLastSent = $date1->diffInDays($date2);
+            $monthsSinceLastSent = $date1->diffInMonths($date2);
 
             if ($daysSinceLastSent == 0) {
                 return false;