From d2cd425ad0fd757cf4940a8a69a0abad05dc4d25 Mon Sep 17 00:00:00 2001
From: Magne Sjaastad <magne.sjaastad@ceetronsolutions.com>
Date: Thu, 7 Nov 2024 11:38:58 +0100
Subject: [PATCH] 11867 Do not assume that the first reported time step is
 initial time step

---
 .../FileInterface/RifEclipseOutputFileTools.cpp              | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/ApplicationLibCode/FileInterface/RifEclipseOutputFileTools.cpp b/ApplicationLibCode/FileInterface/RifEclipseOutputFileTools.cpp
index 06a234a61f..f7af8534ae 100644
--- a/ApplicationLibCode/FileInterface/RifEclipseOutputFileTools.cpp
+++ b/ApplicationLibCode/FileInterface/RifEclipseOutputFileTools.cpp
@@ -260,7 +260,10 @@ void RifEclipseOutputFileTools::timeSteps( const ecl_file_type*    ecl_file,
         int    dayValue       = cvf::Math::floor( dayDoubleValue );
         if ( useStartOfSimulationDate )
         {
-            reportDateTime = reportDateTime.addDays( dayValue );
+            // Do not assume the first day value is zero. Adjust the day value to be relative to the first day value
+            // https://github.com/OPM/ResInsight/issues/11867
+            const int adjustedDayValue = dayValue - dayValues.front();
+            reportDateTime             = reportDateTime.addDays( adjustedDayValue );
         }
 
         double dayFraction  = dayDoubleValue - dayValue;