diff --git a/src/Service/TimeEntryExportService.php b/src/Service/TimeEntryExportService.php
new file mode 100644
index 0000000..f078f3a
--- /dev/null
+++ b/src/Service/TimeEntryExportService.php
@@ -0,0 +1,314 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Service;
+
+use App\Entity\TimeEntry;
+use DateTimeImmutable;
+use PhpOffice\PhpSpreadsheet\Cell\Coordinate;
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+use PhpOffice\PhpSpreadsheet\Worksheet\Worksheet;
+use PhpOffice\PhpSpreadsheet\Writer\Xlsx;
+
+use function count;
+
+class TimeEntryExportService
+{
+    private const array DETAIL_HEADERS = [
+        'Date', 'Utilisateur', 'Projet', 'Tâche', 'Titre',
+        'Tags', 'Début', 'Fin', 'Durée (h)', 'Description',
+    ];
+
+    private const array MONTH_NAMES = [
+        1 => 'Janvier', 2 => 'Février', 3 => 'Mars', 4 => 'Avril',
+        5 => 'Mai', 6 => 'Juin', 7 => 'Juillet', 8 => 'Août',
+        9 => 'Septembre', 10 => 'Octobre', 11 => 'Novembre', 12 => 'Décembre',
+    ];
+
+    /**
+     * @param TimeEntry[] $timeEntries
+     *
+     * @return string Path to the generated temp file
+     */
+    public function generate(array $timeEntries, DateTimeImmutable $from, DateTimeImmutable $to): string
+    {
+        $spreadsheet = new Spreadsheet();
+
+        $this->buildDetailSheet($spreadsheet, $timeEntries);
+        $this->buildProjectRecapSheet($spreadsheet, $timeEntries);
+        $this->buildMonthRecapSheet($spreadsheet, $timeEntries, $from, $to);
+
+        $spreadsheet->setActiveSheetIndex(0);
+
+        $tempFile = tempnam(sys_get_temp_dir(), 'export_temps_').'.xlsx';
+        $writer   = new Xlsx($spreadsheet);
+        $writer->save($tempFile);
+
+        return $tempFile;
+    }
+
+    /**
+     * @param TimeEntry[] $timeEntries
+     */
+    private function buildDetailSheet(Spreadsheet $spreadsheet, array $timeEntries): void
+    {
+        $sheet = $spreadsheet->getActiveSheet();
+        $sheet->setTitle('Détail');
+
+        // Headers
+        foreach (self::DETAIL_HEADERS as $col => $header) {
+            $colLetter = Coordinate::stringFromColumnIndex($col + 1);
+            $sheet->setCellValue("{$colLetter}1", $header);
+        }
+        $this->boldRow($sheet, 1, count(self::DETAIL_HEADERS));
+
+        // Data rows
+        $row = 2;
+        foreach ($timeEntries as $entry) {
+            $duration  = $this->computeDuration($entry);
+            $task      = $entry->getTask();
+            $taskLabel = '';
+            if (null !== $task) {
+                $project   = $task->getProject();
+                $code      = $project?->getCode() ?? '';
+                $taskLabel = $code.'-'.$task->getNumber().' - '.$task->getTitle();
+            }
+
+            $tagLabels = $entry->getTags()->map(fn ($t) => $t->getLabel() ?? '')->toArray();
+
+            $sheet->setCellValue("A{$row}", $entry->getStartedAt()->format('Y-m-d'));
+            $sheet->setCellValue("B{$row}", $entry->getUser()?->getUsername() ?? '');
+            $sheet->setCellValue("C{$row}", $entry->getProject()?->getName() ?? '');
+            $sheet->setCellValue("D{$row}", $taskLabel);
+            $sheet->setCellValue("E{$row}", $entry->getTitle() ?? '');
+            $sheet->setCellValue("F{$row}", implode(', ', $tagLabels));
+            $sheet->setCellValue("G{$row}", $entry->getStartedAt()->format('H:i'));
+            $sheet->setCellValue("H{$row}", $entry->getStoppedAt()?->format('H:i') ?? '');
+            $sheet->setCellValue("I{$row}", round($duration, 2));
+            $sheet->setCellValue("J{$row}", $entry->getDescription() ?? '');
+
+            ++$row;
+        }
+
+        // Total row
+        if ($row > 2) {
+            $sheet->setCellValue("H{$row}", 'Total');
+            $sheet->getStyle("H{$row}")->getFont()->setBold(true);
+            $sheet->setCellValue("I{$row}", '=SUM(I2:I'.($row - 1).')');
+            $sheet->getStyle("I{$row}")->getFont()->setBold(true);
+        }
+
+        // Auto-size columns
+        foreach (range('A', 'J') as $col) {
+            $sheet->getColumnDimension($col)->setAutoSize(true);
+        }
+    }
+
+    /**
+     * @param TimeEntry[] $timeEntries
+     */
+    private function buildProjectRecapSheet(Spreadsheet $spreadsheet, array $timeEntries): void
+    {
+        $sheet = $spreadsheet->createSheet();
+        $sheet->setTitle('Récap par projet');
+
+        // Aggregate: user → project → hours
+        $data     = [];
+        $projects = [];
+        $users    = [];
+
+        foreach ($timeEntries as $entry) {
+            $userName    = $entry->getUser()?->getUsername() ?? 'Inconnu';
+            $projectName = $entry->getProject()?->getName() ?? 'Sans projet';
+            $duration    = $this->computeDuration($entry);
+
+            $users[$userName]              = true;
+            $projects[$projectName]        = true;
+            $data[$userName][$projectName] = ($data[$userName][$projectName] ?? 0) + $duration;
+        }
+
+        ksort($users);
+        ksort($projects);
+        $projectList = array_keys($projects);
+        $userList    = array_keys($users);
+
+        // Headers
+        $sheet->setCellValue('A1', 'Utilisateur');
+        $col = 2;
+        foreach ($projectList as $project) {
+            $letter = Coordinate::stringFromColumnIndex($col);
+            $sheet->setCellValue("{$letter}1", $project);
+            ++$col;
+        }
+        $totalLetter = Coordinate::stringFromColumnIndex($col);
+        $sheet->setCellValue("{$totalLetter}1", 'Total');
+        $this->boldRow($sheet, 1, $col);
+
+        // Data rows
+        $row = 2;
+        foreach ($userList as $user) {
+            $sheet->setCellValue("A{$row}", $user);
+            $col       = 2;
+            $userTotal = 0;
+            foreach ($projectList as $project) {
+                $val    = round($data[$user][$project] ?? 0, 2);
+                $letter = Coordinate::stringFromColumnIndex($col);
+                $sheet->setCellValue("{$letter}{$row}", $val);
+                $userTotal += $val;
+                ++$col;
+            }
+            $letter = Coordinate::stringFromColumnIndex($col);
+            $sheet->setCellValue("{$letter}{$row}", round($userTotal, 2));
+            $sheet->getStyle("{$letter}{$row}")->getFont()->setBold(true);
+            ++$row;
+        }
+
+        // Total row
+        $sheet->setCellValue("A{$row}", 'Total');
+        $sheet->getStyle("A{$row}")->getFont()->setBold(true);
+        $col = 2;
+        foreach ($projectList as $project) {
+            $projectTotal = 0;
+            foreach ($userList as $user) {
+                $projectTotal += $data[$user][$project] ?? 0;
+            }
+            $letter = Coordinate::stringFromColumnIndex($col);
+            $sheet->setCellValue("{$letter}{$row}", round($projectTotal, 2));
+            $sheet->getStyle("{$letter}{$row}")->getFont()->setBold(true);
+            ++$col;
+        }
+        // Grand total
+        $grandTotal = 0;
+        foreach ($data as $userData) {
+            foreach ($userData as $hours) {
+                $grandTotal += $hours;
+            }
+        }
+        $letter = Coordinate::stringFromColumnIndex($col);
+        $sheet->setCellValue("{$letter}{$row}", round($grandTotal, 2));
+        $sheet->getStyle("{$letter}{$row}")->getFont()->setBold(true);
+
+        // Auto-size
+        for ($c = 1; $c <= $col; ++$c) {
+            $sheet->getColumnDimension(Coordinate::stringFromColumnIndex($c))->setAutoSize(true);
+        }
+    }
+
+    /**
+     * @param TimeEntry[] $timeEntries
+     */
+    private function buildMonthRecapSheet(Spreadsheet $spreadsheet, array $timeEntries, DateTimeImmutable $from, DateTimeImmutable $to): void
+    {
+        $sheet = $spreadsheet->createSheet();
+        $sheet->setTitle('Récap par mois');
+
+        // Build month columns from the date range
+        $months  = [];
+        $current = $from->modify('first day of this month');
+        $end     = $to->modify('first day of this month');
+        while ($current <= $end) {
+            $key          = $current->format('Y-m');
+            $label        = self::MONTH_NAMES[(int) $current->format('n')].' '.$current->format('Y');
+            $months[$key] = $label;
+            $current      = $current->modify('+1 month');
+        }
+
+        // Aggregate: user → month-key → hours
+        $data  = [];
+        $users = [];
+
+        foreach ($timeEntries as $entry) {
+            $userName = $entry->getUser()?->getUsername() ?? 'Inconnu';
+            $monthKey = $entry->getStartedAt()->format('Y-m');
+            $duration = $this->computeDuration($entry);
+
+            $users[$userName]           = true;
+            $data[$userName][$monthKey] = ($data[$userName][$monthKey] ?? 0) + $duration;
+        }
+
+        ksort($users);
+        $userList  = array_keys($users);
+        $monthKeys = array_keys($months);
+
+        // Headers
+        $sheet->setCellValue('A1', 'Utilisateur');
+        $col = 2;
+        foreach ($months as $label) {
+            $letter = Coordinate::stringFromColumnIndex($col);
+            $sheet->setCellValue("{$letter}1", $label);
+            ++$col;
+        }
+        $totalLetter = Coordinate::stringFromColumnIndex($col);
+        $sheet->setCellValue("{$totalLetter}1", 'Total');
+        $this->boldRow($sheet, 1, $col);
+
+        // Data rows
+        $row = 2;
+        foreach ($userList as $user) {
+            $sheet->setCellValue("A{$row}", $user);
+            $col       = 2;
+            $userTotal = 0;
+            foreach ($monthKeys as $monthKey) {
+                $val    = round($data[$user][$monthKey] ?? 0, 2);
+                $letter = Coordinate::stringFromColumnIndex($col);
+                $sheet->setCellValue("{$letter}{$row}", $val);
+                $userTotal += $val;
+                ++$col;
+            }
+            $letter = Coordinate::stringFromColumnIndex($col);
+            $sheet->setCellValue("{$letter}{$row}", round($userTotal, 2));
+            $sheet->getStyle("{$letter}{$row}")->getFont()->setBold(true);
+            ++$row;
+        }
+
+        // Total row
+        $sheet->setCellValue("A{$row}", 'Total');
+        $sheet->getStyle("A{$row}")->getFont()->setBold(true);
+        $col = 2;
+        foreach ($monthKeys as $monthKey) {
+            $monthTotal = 0;
+            foreach ($userList as $user) {
+                $monthTotal += $data[$user][$monthKey] ?? 0;
+            }
+            $letter = Coordinate::stringFromColumnIndex($col);
+            $sheet->setCellValue("{$letter}{$row}", round($monthTotal, 2));
+            $sheet->getStyle("{$letter}{$row}")->getFont()->setBold(true);
+            ++$col;
+        }
+        $grandTotal = 0;
+        foreach ($data as $userData) {
+            foreach ($userData as $hours) {
+                $grandTotal += $hours;
+            }
+        }
+        $letter = Coordinate::stringFromColumnIndex($col);
+        $sheet->setCellValue("{$letter}{$row}", round($grandTotal, 2));
+        $sheet->getStyle("{$letter}{$row}")->getFont()->setBold(true);
+
+        // Auto-size
+        for ($c = 1; $c <= $col; ++$c) {
+            $sheet->getColumnDimension(Coordinate::stringFromColumnIndex($c))->setAutoSize(true);
+        }
+    }
+
+    private function computeDuration(TimeEntry $entry): float
+    {
+        $start = $entry->getStartedAt();
+        $end   = $entry->getStoppedAt();
+
+        if (null === $start || null === $end) {
+            return 0;
+        }
+
+        return ($end->getTimestamp() - $start->getTimestamp()) / 3600;
+    }
+
+    private function boldRow(Worksheet $sheet, int $row, int $colCount): void
+    {
+        for ($c = 1; $c <= $colCount; ++$c) {
+            $letter = Coordinate::stringFromColumnIndex($c);
+            $sheet->getStyle("{$letter}{$row}")->getFont()->setBold(true);
+        }
+    }
+}