diff --git a/opm/input/eclipse/Schedule/Schedule.hpp b/opm/input/eclipse/Schedule/Schedule.hpp
index 5d740fbe7..d5faad6c0 100644
--- a/opm/input/eclipse/Schedule/Schedule.hpp
+++ b/opm/input/eclipse/Schedule/Schedule.hpp
@@ -20,22 +20,21 @@
 #define SCHEDULE_HPP
 
 #include <cstddef>
+#include <ctime>
 #include <map>
 #include <memory>
 #include <optional>
-#include <ostream>
+#include <iosfwd>
 #include <string>
 #include <unordered_map>
-#include <unordered_set>
 #include <utility>
 #include <vector>
 
-#include <time.h>
-
 #include <opm/input/eclipse/EclipseState/Runspec.hpp>
+#include <opm/input/eclipse/Parser/InputErrorAction.hpp>
+#include <opm/input/eclipse/Python/Python.hpp>
 #include <opm/input/eclipse/Schedule/GasLiftOpt.hpp>
 #include <opm/input/eclipse/Schedule/Group/Group.hpp>
-#include <opm/input/eclipse/Schedule/Group/GTNode.hpp>
 #include <opm/input/eclipse/Schedule/Group/GuideRateConfig.hpp>
 #include <opm/input/eclipse/Schedule/MessageLimits.hpp>
 #include <opm/input/eclipse/Schedule/Network/ExtNetwork.hpp>
@@ -45,18 +44,10 @@
 #include <opm/input/eclipse/Schedule/Well/PAvg.hpp>
 #include <opm/input/eclipse/Schedule/Well/Well.hpp>
 #include <opm/input/eclipse/Schedule/Well/WellTestConfig.hpp>
-#include <opm/input/eclipse/Schedule/Well/WellMatcher.hpp>
 #include <opm/input/eclipse/Schedule/WriteRestartFileEvents.hpp>
 #include <opm/input/eclipse/Schedule/CompletedCells.hpp>
-#include <opm/input/eclipse/Schedule/ScheduleDeck.hpp>
-#include <opm/input/eclipse/Schedule/ScheduleState.hpp>
-#include <opm/input/eclipse/Schedule/RPTConfig.hpp>
 #include <opm/input/eclipse/Schedule/Action/SimulatorUpdate.hpp>
 #include <opm/input/eclipse/Schedule/Action/WGNames.hpp>
-#include <opm/input/eclipse/Parser/ParseContext.hpp>
-
-#include <opm/input/eclipse/Python/Python.hpp>
-
 #include <opm/input/eclipse/Units/UnitSystem.hpp>
 
 namespace Opm
@@ -67,11 +58,13 @@ namespace Opm
     class DeckRecord;
     class EclipseState;
     class FieldPropsManager;
+    class GTNode;
     class ParseContext;
     class SCHEDULESection;
     class SummaryState;
     class ErrorGuard;
     class UDQConfig;
+    class WellMatcher;
 
     namespace RestartIO { struct RstState; }
 
@@ -213,10 +206,10 @@ namespace Opm
          * If the input deck does not specify a start time, Eclipse's 1. Jan
          * 1983 is defaulted
          */
-        time_t getStartTime() const;
-        time_t posixStartTime() const;
-        time_t posixEndTime() const;
-        time_t simTime(std::size_t timeStep) const;
+        std::time_t getStartTime() const;
+        std::time_t posixStartTime() const;
+        std::time_t posixEndTime() const;
+        std::time_t simTime(std::size_t timeStep) const;
         double seconds(std::size_t timeStep) const;
         double stepLength(std::size_t timeStep) const;
         std::optional<int> exitStatus() const;
diff --git a/src/opm/input/eclipse/Schedule/Schedule.cpp b/src/opm/input/eclipse/Schedule/Schedule.cpp
index a42c2a150..97e7017cf 100644
--- a/src/opm/input/eclipse/Schedule/Schedule.cpp
+++ b/src/opm/input/eclipse/Schedule/Schedule.cpp
@@ -68,6 +68,7 @@
 #include <opm/input/eclipse/Schedule/MSW/WellSegments.hpp>
 #include <opm/input/eclipse/Schedule/Group/GConSump.hpp>
 #include <opm/input/eclipse/Schedule/Group/GConSale.hpp>
+#include <opm/input/eclipse/Schedule/Group/GTNode.hpp>
 
 #include <opm/input/eclipse/Schedule/OilVaporizationProperties.hpp>
 #include <opm/input/eclipse/Schedule/UDQ/UDQConfig.hpp>
@@ -294,11 +295,11 @@ Schedule::Schedule(const Deck& deck, const EclipseState& es, const std::optional
         return this->posixStartTime( );
     }
 
-    time_t Schedule::posixStartTime() const {
+    std::time_t Schedule::posixStartTime() const {
         return std::chrono::system_clock::to_time_t(this->m_sched_deck[0].start_time());
     }
 
-    time_t Schedule::posixEndTime() const {
+    std::time_t Schedule::posixEndTime() const {
         // This should indeed access the start_time() property of the last
         // snapshot.
         return std::chrono::system_clock::to_time_t(this->snapshots.back().start_time());
@@ -1257,7 +1258,7 @@ File {} line {}.)", pattern, location.keyword, location.filename, location.linen
         return std::chrono::duration_cast<std::chrono::seconds>(elapsed).count();
     }
 
-    time_t Schedule::simTime(std::size_t timeStep) const {
+    std::time_t Schedule::simTime(std::size_t timeStep) const {
         return std::chrono::system_clock::to_time_t( this->snapshots[timeStep].start_time() );
     }
 
diff --git a/tests/parser/ScheduleTests.cpp b/tests/parser/ScheduleTests.cpp
index 8b85d41e6..ad990b8eb 100644
--- a/tests/parser/ScheduleTests.cpp
+++ b/tests/parser/ScheduleTests.cpp
@@ -71,6 +71,7 @@
 #include <opm/input/eclipse/Schedule/Well/WellInjectionProperties.hpp>
 #include <opm/input/eclipse/Schedule/Group/GuideRateConfig.hpp>
 #include <opm/input/eclipse/Schedule/Group/GuideRate.hpp>
+#include <opm/input/eclipse/Schedule/Group/GTNode.hpp>
 #include <opm/input/eclipse/Schedule/CompletedCells.hpp>
 #include <opm/input/eclipse/Schedule/ScheduleGrid.hpp>