diff --git a/src/importer/features/main/index.tsx b/src/importer/features/main/index.tsx
index c2a8351f..8222dd69 100644
--- a/src/importer/features/main/index.tsx
+++ b/src/importer/features/main/index.tsx
@@ -152,7 +152,20 @@ export default function Main(props: CSVImporterProps) {
                     break;
                   case "xlsx":
                   case "xls":
-                    const workbook = XLSX.read(bstr as string, { type: "binary" });
+                    const workbook = XLSX.read(bstr as string, { type: "binary", cellDates: true });
+                    for (const sheetName of workbook.SheetNames) {
+                      const sheet = workbook.Sheets[sheetName];
+                      for (const [cellRef, cell] of Object.entries(sheet)) {
+                        // skip metadata
+                        if (cellRef.startsWith("!")) continue;   
+
+                        // only process date cells
+                        if (cell.t !== "d") continue; 
+                    
+                        // Force format into YYYY-MM-DD
+                        cell.v = XLSX.SSF.format("yyyy-mm-dd", cell.v);
+                      }
+                    }
                     const sheetList = workbook.SheetNames;
                     const data = XLSX.utils.sheet_to_json(workbook.Sheets[sheetList[0]], { header: 1 }) as Array<Array<string>>;
                     const rows: FileRow[] = data.filter(isNotBlankRow).map((row: string[], index: number) => ({ index, values: row }));