下面是具体的实现代码：
sqlite> SELECT datetime(1377168853, 'unixepoch', 'localtime');
+------------------------------------------------+
| datetime(1377168853, 'unixepoch', 'localtime') |
+------------------------------------------------+
| 2013-08-22 18:54:13 |
+------------------------------------------------+
1 row in set
sqlite> SELECT strftime('%s','now');
+----------------------+
| strftime('%s','now') |
+----------------------+
| 1380728519 |
+----------------------+
1 row in set
sqlite> SELECT datetime('now');
+---------------------+
| datetime('now') |
+---------------------+
| 2013-10-02 15:40:44 |
+---------------------+
1 row in set
