二次重构，加入预设模板

src/data_access.py

@@ -170,8 +170,26 @@ class DataAccessLayer:
         # 尝试转换为日期时间
         if col_data.dtype == 'object':
             try:
-                pd.to_datetime(col_data.dropna().head(100))
-                return 'datetime'
+                sample = col_data.dropna().head(20)
+                if len(sample) == 0:
+                    pass
+                else:
+                    # 尝试用常见日期格式解析
+                    date_formats = ['%Y-%m-%d', '%Y/%m/%d', '%Y-%m-%d %H:%M:%S', '%Y/%m/%d %H:%M:%S', '%d/%m/%Y', '%m/%d/%Y']
+                    parsed = False
+                    for fmt in date_formats:
+                        try:
+                            pd.to_datetime(sample, format=fmt)
+                            parsed = True
+                            break
+                        except (ValueError, TypeError):
+                            continue
+                    if not parsed:
+                        # 最后尝试自动推断，但用 infer_datetime_format
+                        pd.to_datetime(sample, format='mixed', dayfirst=False)
+                        parsed = True
+                    if parsed:
+                        return 'datetime'
             except:
                 pass