diff --git a/src/View/BoundaryCondition/Edit/Table.py b/src/View/BoundaryCondition/Edit/Table.py
index d4e981df..bbde866e 100644
--- a/src/View/BoundaryCondition/Edit/Table.py
+++ b/src/View/BoundaryCondition/Edit/Table.py
@@ -98,7 +98,7 @@ class TableModel(PamhyrTableModel):
                     value = timestamp_to_old_pamhyr_date(int(v))
                 else:
                     value = format_datetime(
-                        self._start_date + timedelta(seconds=float(v))
+                        datetime(1970, 1, 1) + timedelta(seconds=float(v))
                     )
             else:
                 value = f"{v}"
@@ -118,7 +118,7 @@ class TableModel(PamhyrTableModel):
         try:
             if (self._data.header[column] == "time"
                     and self._opt_data == "date"):
-                value = self.date_to_elapsed_seconds(value)
+                value = self.date_to_timestamp(value)
 
             row = self.get_true_data_row(row)
 
diff --git a/src/View/BoundaryConditionsAdisTS/Edit/Table.py b/src/View/BoundaryConditionsAdisTS/Edit/Table.py
index e6c714d8..99c82c9f 100644
--- a/src/View/BoundaryConditionsAdisTS/Edit/Table.py
+++ b/src/View/BoundaryConditionsAdisTS/Edit/Table.py
@@ -88,7 +88,7 @@ class TableModel(PamhyrTableModel):
                     value = timestamp_to_old_pamhyr_date(int(v))
                 else:
                     value = format_datetime(
-                        self._start_date + timedelta(seconds=float(v))
+                        datetime(1970, 1, 1) + timedelta(seconds=float(v))
                     )
             else:
                 value = f"{v}"
@@ -108,7 +108,7 @@ class TableModel(PamhyrTableModel):
         try:
             if (self._data.header[column] == "time"
                     and self._opt_data == "date"):
-                value = self.date_to_elapsed_seconds(value)
+                value = self.date_to_timestamp(value)
 
             row = self.get_true_data_row(row)
 
diff --git a/src/View/BoundaryConditionsTemperature/Edit/Table.py b/src/View/BoundaryConditionsTemperature/Edit/Table.py
index 196d68d7..7854d91a 100644
--- a/src/View/BoundaryConditionsTemperature/Edit/Table.py
+++ b/src/View/BoundaryConditionsTemperature/Edit/Table.py
@@ -88,7 +88,7 @@ class TableModel(PamhyrTableModel):
                     value = timestamp_to_old_pamhyr_date(int(v))
                 else:
                     value = format_datetime(
-                        self._start_date + timedelta(seconds=float(v))
+                        datetime(1970, 1, 1) + timedelta(seconds=float(v))
                     )
             else:
                 value = f"{v}"
@@ -108,7 +108,7 @@ class TableModel(PamhyrTableModel):
         try:
             if (self._data.header[column] == "time"
                     and self._opt_data == "date"):
-                value = self.date_to_elapsed_seconds(value)
+                value = self.date_to_timestamp(value)
 
             row = self.get_true_data_row(row)
 
diff --git a/src/View/LateralContribution/Edit/Table.py b/src/View/LateralContribution/Edit/Table.py
index 289b0265..94b2c39f 100644
--- a/src/View/LateralContribution/Edit/Table.py
+++ b/src/View/LateralContribution/Edit/Table.py
@@ -77,7 +77,7 @@ class TableModel(PamhyrTableModel):
                     value = timestamp_to_old_pamhyr_date(int(v))
                 else:
                     value = format_datetime(
-                        self._start_date + timedelta(seconds=float(v))
+                        datetime(1970, 1, 1) + timedelta(seconds=float(v))
                     )
             else:
                 value = f"{v}"
@@ -97,7 +97,7 @@ class TableModel(PamhyrTableModel):
         try:
             if (self._data.header[column] == "time"
                     and self._opt_data == "date"):
-                value = self.date_to_elapsed_seconds(value)
+                value = self.date_to_timestamp(value)
 
             self._undo.push(
                 SetDataCommand(
diff --git a/src/View/LateralContributionsAdisTS/Edit/Table.py b/src/View/LateralContributionsAdisTS/Edit/Table.py
index eacd21b1..d055be64 100644
--- a/src/View/LateralContributionsAdisTS/Edit/Table.py
+++ b/src/View/LateralContributionsAdisTS/Edit/Table.py
@@ -91,7 +91,7 @@ class TableModel(PamhyrTableModel):
                     value = timestamp_to_old_pamhyr_date_adists(int(v))
                 else:
                     value = format_datetime(
-                        self._start_date + timedelta(seconds=float(v))
+                        datetime(1970, 1, 1) + timedelta(seconds=float(v))
                     )
             else:
                 value = f"{v}"
@@ -111,7 +111,7 @@ class TableModel(PamhyrTableModel):
         try:
             if (self._data.header[column] == "time"
                     and self._opt_data == "date"):
-                value = self.date_to_elapsed_seconds(value)
+                value = self.date_to_timestamp(value)
 
             row = self.get_true_data_row(row)
 
diff --git a/src/View/Tools/PamhyrTable.py b/src/View/Tools/PamhyrTable.py
index a3196f97..5ba5b5d2 100644
--- a/src/View/Tools/PamhyrTable.py
+++ b/src/View/Tools/PamhyrTable.py
@@ -18,6 +18,7 @@
 
 import logging
 import traceback
+from datetime import timezone
 
 from tools import trace, timer, parse_datetime
 
@@ -62,8 +63,8 @@ class PamhyrTextDelegate(QStyledItemDelegate):
 
 
 class PamhyrTableModel(QAbstractTableModel):
-    def date_to_elapsed_seconds(self, value):
-        """Convert an entered date to seconds since the study start date."""
+    def date_to_timestamp(self, value):
+        """Convert an accepted calendar date to its raw UTC timestamp."""
         try:
             entered_date = parse_datetime(value)
         except ValueError as error:
@@ -81,7 +82,7 @@ class PamhyrTableModel(QAbstractTableModel):
             )
             raise error
 
-        return (entered_date - self._start_date).total_seconds()
+        return entered_date.replace(tzinfo=timezone.utc).timestamp()
 
     def _setup_delegates(self):
         if self._table_view is None:
diff --git a/src/View/WeatherParameters/Edit/Table.py b/src/View/WeatherParameters/Edit/Table.py
index 2a9c8754..91e3ca0f 100644
--- a/src/View/WeatherParameters/Edit/Table.py
+++ b/src/View/WeatherParameters/Edit/Table.py
@@ -78,7 +78,7 @@ class TableModel(PamhyrTableModel):
                     value = timestamp_to_old_pamhyr_date(int(v))
                 else:
                     value = format_datetime(
-                        self._start_date + timedelta(seconds=float(v))
+                        datetime(1970, 1, 1) + timedelta(seconds=float(v))
                     )
             else:
                 value = f"{v}"
@@ -98,7 +98,7 @@ class TableModel(PamhyrTableModel):
         try:
             if (self._data.header[column] == "time"
                     and self._opt_data == "date"):
-                value = self.date_to_elapsed_seconds(value)
+                value = self.date_to_timestamp(value)
 
             self._undo.push(
                 SetDataCommand(