Bug #78149 TIMESTAMPDIFF vs TIMESTAMPADD and DATE_ADD : count months in different way
Submitted: 20 Aug 2015 11:02 Modified: 20 Aug 2015 19:06
Reporter: Sergey Dudchenko Email Updates:
Status: Verified Impact on me:
None 
Category:MySQL Server: DML Severity:S3 (Non-critical)
Version:5.0/5.1/5.5/5.6/5.7 OS:Ubuntu
Assigned to: CPU Architecture:Any

[20 Aug 2015 11:02] Sergey Dudchenko
Description:
Functions TIMESTAMPDIFF and DATE_ADD counts months in different way when in the next month less days than in original date. 
For example, let's take February 2016:
Select TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00');
// Returns 5 but correct value is 6.
Select TIMESTAMPADD (MONTH,6,'2015-08-30 11:10:00');
// Returns correct date 2016-02-29 11:10:00
Select DATE_ADD('2015-08-30 11:10:00', INTERVAL 6 MONTH);
// Returns correct date 2016-02-29 11:10:00

This inconsistence in approaches doesn't allow developers use them together and they have to create own unnecessary code.

How to repeat:
Select TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00');
// Returns 5 but correct value is 6.
Select DATE_ADD('2015-08-30 11:10:00', INTERVAL 6 MONTH);
// Returns correct date 2016-02-29 11:10:00

Another example:
Select TIMESTAMPDIFF(MONTH,'2015-08-31 11:10:00','2015-09-30 12:40:00');
// Returns 0 but correct value is 1.
Select TIMESTAMPADD (MONTH,1,'2015-08-31 11:10:00');
// Returns 2015-09-30 11:10:00
Select DATE_ADD('2015-08-31 11:10:00', INTERVAL 1 MONTH);
// Returns 2015-09-30 11:10:00

Suggested fix:
Fix TIMESTAMPDIFF function in counting calendar months
[20 Aug 2015 19:06] Godofredo Miguel Solorzano
Thank you for the bug report.

C:\dbs>c:\dbs\5.0\bin\mysql -uroot --port=3500 --prompt="mysql 5.0 > "
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.0.97-Win X64 Source distribution

Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql 5.0 > Select TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00');
+------------------------------------------------------------------+
| TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00') |
+------------------------------------------------------------------+
|                                                                5 |
+------------------------------------------------------------------+
1 row in set (0.00 sec)

C:\dbs>c:\dbs\5.1\bin\mysql -uroot --port=3510 --debug-info --prompt="mysql 5.1 > "
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 2
Server version: 5.1.74-Win X64 Source distribution

Copyright (c) 2000, 2013, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql 5.1 > Select TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00');
+------------------------------------------------------------------+
| TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00') |
+------------------------------------------------------------------+
|                                                                5 |
+------------------------------------------------------------------+
1 row in set (0.00 sec)

C:\dbs>c:\dbs\5.5\bin\mysql -uroot --port=3550 --prompt="mysql 5.5 > "
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 1
Server version: 5.5.46-log Source distribution PULL: 2015/08/14

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql 5.5 > Select TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00');
+------------------------------------------------------------------+
| TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00') |
+------------------------------------------------------------------+
|                                                                5 |
+------------------------------------------------------------------+
1 row in set (0.00 sec)

C:\dbs>c:\dbs\5.6\bin\mysql -uroot --port=3560 -p --prompt="mysql 5.6 > "
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.6.27 Source distribution PULL: 2015/08/14

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql 5.6 > Select TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00');
+------------------------------------------------------------------+
| TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00') |
+------------------------------------------------------------------+
|                                                                5 |
+------------------------------------------------------------------+
1 row in set (0.11 sec)

C:\dbs>c:\dbs\5.7\bin\mysql -uroot -p --port=3570 --prompt="mysql 5.7 > "
Enter password: ******
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5
Server version: 5.7.9 Source distribution PULL 2015/08/14

Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql 5.7 > Select TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00');
+------------------------------------------------------------------+
| TIMESTAMPDIFF(MONTH,'2015-08-30 11:10:00','2016-02-29 12:40:00') |
+------------------------------------------------------------------+
|                                                                5 |
+------------------------------------------------------------------+