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Editorial Team
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Asked: 2026-05-14T05:29:47+00:00

Since TIMESTAMP in mysql is stored as a 32bit value representing the time interval

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Since TIMESTAMP in mysql is stored as a 32bit value representing the time interval from 1970-jan-1 0:00:00 in seconds, I assumed that using minus (-) operator on TIMESTAMP values would give the difference of these values in seconds. Actually not:

+---------------------------------------------------------------------+
| TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:29:59") |
+---------------------------------------------------------------------+
| 41.000000                                                           |
+---------------------------------------------------------------------+
1 row in set (0.05 sec)

mysql> select timestampdiff(SECOND,TIMESTAMP("2010-04-02 10:30:00"),TIMESTAMP("2010-04-02 10:29:59"));
+-----------------------------------------------------------------------------------------+
| timestampdiff(SECOND,TIMESTAMP("2010-04-02 10:30:00"),TIMESTAMP("2010-04-02 10:29:59")) |
+-----------------------------------------------------------------------------------------+
| -1                                                                                      |
+-----------------------------------------------------------------------------------------+

mysql> select TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:30:01") ;
+---------------------------------------------------------------------+
| TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:30:01") |
+---------------------------------------------------------------------+
| -1.000000                                                           |
+---------------------------------------------------------------------+

+---------------------------------------------------------------------+
| TIMESTAMP("2010-04-02 10:30:00") - TIMESTAMP("2010-04-02 10:31:00") |
+---------------------------------------------------------------------+
| -100.000000                                                         |
+---------------------------------------------------------------------+

It seems like one minute difference is 100 instead of 60.

Why is this?

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1 Answer

  1. Editorial Team

    Just a wild guess, but maybe you’re casting the strings to an integer in three of the cases?

    20100402103000 – 20100402103100 = -100

    20100402103000 – 20100402103001 = -1

    20100402103000 – 20100402102959 = 41

    The other case does the conversion properly.

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