diff --git a/BMA.EHR.Domain/Extensions/DateTimeExtension.cs b/BMA.EHR.Domain/Extensions/DateTimeExtension.cs
index 985327de..6c536239 100644
--- a/BMA.EHR.Domain/Extensions/DateTimeExtension.cs
+++ b/BMA.EHR.Domain/Extensions/DateTimeExtension.cs
@@ -126,7 +126,11 @@ namespace BMA.EHR.Domain.Extensions
                     if (currentDate.Day < date.Day)
                     {
                         months--;
-                        int lastMonthDays = DateTime.DaysInMonth(currentDate.Year, currentDate.Month - 1);
+                        int lastMonthDays = 0;
+                        if (currentDate.Month == 1)
+                            lastMonthDays = DateTime.DaysInMonth(currentDate.Year - 1, 12);
+                        else
+                            lastMonthDays = DateTime.DaysInMonth(currentDate.Year, currentDate.Month - 1);
                         days = lastMonthDays - date.Day + currentDate.Day;
                     }
                     else
@@ -141,7 +145,11 @@ namespace BMA.EHR.Domain.Extensions
                     if (currentDate.Day < date.Day)
                     {
                         months--;
-                        int lastMonthDays = DateTime.DaysInMonth(currentDate.Year, currentDate.Month - 1);
+                        int lastMonthDays = 0;
+                        if (currentDate.Month == 1)
+                            lastMonthDays = DateTime.DaysInMonth(currentDate.Year - 1, 12);
+                        else
+                            lastMonthDays = DateTime.DaysInMonth(currentDate.Year, currentDate.Month - 1);
                         days = lastMonthDays - date.Day + currentDate.Day;
                     }
                     else