Try 5.1.1 fixing some issues on that point.
If you still reproduce, please give more hints :
- browser / version of browser
- OS / version of OS
- current locale (fr, en, ...)
- the standard decimal point in your locale (".", "," or else)

Thanks.

Browser Firefox :42.0
OS Win7
Current FR
standard decimal ","

I'm return to the 5.1.0 version, and it's works.

Do you have any error in browser console ?
Did you try and clean browser cache when testing ?

I just update on the 5.1.2 ... and I cannot have 7,4 h / day !!!! 🙁
It's change all of the real works!

Look on the web browser console :
see attached files

require({cache:{"dijit/_editor/plugins/FontChoice":function(){define(["require","dojo/_base/array","dojo/_base/declare","dojo/dom-construct","dojo/i18n","dojo/_base/lang","dojo/store/Memory","../../registry","../../_Widget","../../

VERSION V5.1.1
2015-11-10 10:05:34.978 ===== TRACE =====
2015-11-10 10:05:35.060 ===== TRACE ===== 0 lines deleted from table "plannedwork".
2015-11-10 10:05:35.277 ===== TRACE ===== 621 lines deleted from table "columnselector".
2015-11-10 10:05:35.298 ** ERROR ** Exception-[23000] SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '21' for key 'PRIMARY'
2015-11-10 10:05:35.298 ** ERROR ** For query : INSERT INTO `planningmode` (`id`, `applyTo`, `name`, `code`, `sortOrder`, `idle`, `mandatoryStartDate`, `mandatoryEndDate`) VALUES
(21, 'TestSession', 'PlanningModeSTART', 'START', 130, 0 , 1, 0);
2015-11-10 10:05:35.298 ** ERROR ** Strack trace :
2015-11-10 10:05:35.298 ** ERROR ** #0 Sql->query called at [/var/www/projeqtor/db/maintenanceFunctions.php:71]
2015-11-10 10:05:35.299 ** ERROR ** #1 runScript called at [/var/www/projeqtor/db/maintenance.php:99]
2015-11-10 10:05:35.299 ** ERROR ** #2 include called at [/var/www/projeqtor/tool/loginCheck.php:117]
2015-11-10 10:05:35.299 ===== TRACE =====
2015-11-10 10:05:35.299 ===== TRACE ===== Error # 1 => SQL error while executing maintenance query for version V5.1.1 (see above message)
2015-11-10 10:05:35.299 ===== TRACE =====
2015-11-10 10:05:35.299 ===== TRACE ===== *************************************************
2015-11-10 10:05:35.299 ===== TRACE =====
2015-11-10 10:05:35.299 ===== TRACE =====
2015-11-10 10:05:35.299 ===== TRACE ===== DATABASE UPDATED
2015-11-10 10:05:35.299 ===== TRACE ===== WITH 1 ERROR
2015-11-10 10:05:35.299 ===== TRACE =====
2015-11-10 10:05:35.713 ===== TRACE ===== =====================================
2015-11-10 10:05:35.713 ===== TRACE =====
2015-11-10 10:05:35.713 ===== TRACE ===== 1 ERRORS DURING UPDATE TO VERSION V5.1.2

Help me please :unsure:

Just comment line 162 in /view/parameter.php

				//  echo ' constraints="{places:'0'}" ';

change it ( add // on 162 line)
disconnect
connect
and i can change the hours/day parameter

I need to remove // on 162 line or not ?

No, keep it.
This option was introduced in V5.1 to forbid decimal data in Global Parameter screen, but as you pointed out, it was a bad idea, so it will be removed in next patch.