diff --git a/class/ukTaxWeek.php b/class/ukTaxWeek.php
index 0d3151c..74c36e9 100644
--- a/class/ukTaxWeek.php
+++ b/class/ukTaxWeek.php
@@ -1,5 +1,5 @@
 <?php
-/* This file is part of the UK Tax Weeks Class found at 
+/* This file is part of the UK Tax Weeks Class found at
  * www.whitehurstmedia.co.uk
  *
  * Copyright (C) 2018 Kay Whitehurst - All Rights Reserved
@@ -10,73 +10,74 @@
  * Please consider appropriate references and credits.
  */
 
-Class UKTaxWeeks
+class UKTaxWeeks
 {
-  
-  function getTaxWeekByDate($wDate,$floorDate = "06/04")
-  {
-    /*
-     * Get the Tax week number based upon $wDate - The date you're querying - 
-     * and optionally $floorDate, which defaults to the UK tax start 
-     * date of 06/04
-     */
-    
-    //because we use the UK date format dd/mm/yyyy, convert this to US mm/dd/yyyy
-    $bits = explode('/',$wDate);
-    $wDate = $bits[1].'/'.$bits[0].'/'.$bits[2];
+    public function getTaxWeekByDate($wDate, $floorDate = '06/04')
+    {
+        /*
+          * Get the Tax week number based upon $wDate - The date you're querying -
+          * and optionally $floorDate, which defaults to the UK tax start
+          * date of 06/04
+          */
 
-    //convert the provided date to a query string/timestamp
-    $qDate = strtotime($wDate);
-    
-    //Calculate This Day, This Month and This Year from current datetime
-    $tDay = date("d",$qDate);
-    $tMonth = date("m",$qDate);    
-    $tYear = date("Y",$qDate);
+        //because we use the UK date format dd/mm/yyyy, convert this to US mm/dd/yyyy
+        $bits = explode('/', $wDate);
+        $wDate = $bits[1].'/'.$bits[0].'/'.$bits[2];
 
-    //Calculate Comparison Day and Comparison Month from floorDate
-    $floorBits = explode('/',$floorDate); 
-    $cDay = $floorBits[0];
-    $cMonth = $floorBits[1];
-    
-    
-    //decide whether the start of the tax year for the given date was this calendar year or last
-    if ($tMonth > $cMonth) {
-      $scenario = 1;
-    } else if ($tMonth == $cMonth) {
-      if ($tDay >= $cDay)
-      {
-        $scenario = 1;
-      } else {
-        $scenario = 2;
-      }
-    } else {
-      $scenario = 2;
-    }
+        //convert the provided date to a query string/timestamp
+        $qDate = strtotime($wDate);
 
-    
+        //Calculate This Day, This Month and This Year from current datetime
+        $tDay = date('d', $qDate);
+        $tMonth = date('m', $qDate);
+        $tYear = date('Y', $qDate);
 
+        //Calculate Comparison Day and Comparison Month from floorDate
+        $floorBits = explode('/', $floorDate);
+        $cDay = $floorBits[0];
+        $cMonth = $floorBits[1];
 
-    if($scenario == 1)
-    {
-      //Today is in year 1 - Start of the tax year is in this calendar year
-      $offset = date("W",strtotime($floorDate . "/" . $tYear));
-      //Week 1 was already $offset weeks into the year. Calculate tax week accordingly
-      $taxWeekNumber = date("W",$qDate) - ($offset - 2);
+        $floorDate = $floorBits[1].'/'.$floorBits[0];
+
+        //decide whether the start of the tax year for the given date was this calendar year or last
+        if ((int) $tMonth > (int) $cMonth) {
+            $scenario = 1;
+        } elseif ($tMonth == $cMonth) {
+            if ($tDay >= $cDay) {
+                $scenario = 1;
+            } else {
+                $scenario = 2;
+            }
+        } elseif ($tMonth < $cMonth) {
+            $scenario = 2;
+        }
+
+        if ($scenario == 1) {
+            //Today is in year 1 - Start of the tax year is in this calendar year
+            $offset = date('W', strtotime($floorDate.'/'.$tYear));
+            //Week 1 was already $offset weeks into the year. Calculate tax week accordingly
+            $taxWeekNumber = date('W', $qDate) - ($offset - 2) - 1;
+        } elseif ($scenario == 2) {
+            //Today is in year 0 - Start of the tax year was in last calendar year
+            $fullYearWeeks = $this->getIsoWeeksInYear($tYear - 1);
 
-    } elseif ($scenario == 2) {
+            $floorWeek = date('W', strtotime($floorDate.'/'.($tYear - 1)));
 
-      //Today is in year 0 - Start of the tax year was in last calendar year
-      $fullYearWeeks = date("W",strtotime("31/12/" . ($tYear - 1)));
-      $floorWeek = date("W",strtotime($floorDate . "/" . ($tYear - 1)));
-      //subtract the base week number from the whole year to account for 53 week years.
-      $offset = $fullYearWeeks - $floorWeek;
-      //calculate previous years weeks (offset) + this year's week count
-      $taxWeekNumber = $offset + date("W",$qDate);
+            //subtract the base week number from the whole year to account for 53 week years.
+            $offset = $fullYearWeeks - $floorWeek;
+
+            //calculate previous years weeks (offset) + this year's week count
+            $taxWeekNumber = $offset + date('W', strtotime("$tMonth/$tDay/$tYear")) - 1;
+        }
+
+        return $taxWeekNumber;
+    }
+
+    public function getIsoWeeksInYear($year)
+    {
+        $date = new DateTime();
+        $date->setISODate($year, 53);
 
+        return $date->format('W') === '53' ? 53 : 52;
     }
-    
-    return $taxWeekNumber;
-  }
-  
 }
-?>