This Question begins Here:

What's not, the goal of this question ?

To be, a « Yet Another Question About Internationalization and Localization ». (This is absolutely not the case).

What is the goal , of this Question ?

Replacing the OpenERP's standard Gregorian Calendar by a Hijri (Islamic) calendar, or giving the possibilitie to the user to choose the calendar he want to use.

Why not, there are probably thousands of OpenERP users around the world, and in many countries, where Gregorian calendar is not used, or at least an other calendar is in use (e,g Ethiopian, Thai, Chinese, Hindu, Hijri, Oromo, Somali, Iranian, Hebrew, Bahá'í … Calendars),

http://en.wikipedia.org/wiki/List_of_calendars

This lead us to a new question : How to change from the OpenERP's standard calendar, to any other calendar ?

Is there any possibilities to do that, in OpenERP, and How to achieve this task (using the OpenObject framework)?

Should us build a new module : Coded in Python or a Web module with JS ...?

Or, should us just modify an existing module ?

Can we do that, without the need of patching the original code , and without breaking it?

How to do this, without having to reinvent the wheel ?

Before going further, we must clarify something, which is for me a crucial point :

The Calendar is just the apparent part of the iceberg, and the hidden parts are, date and Time.

So, How Time, Date, and Calendar are handled in OpenERP ?

1. From this LINK (response from Fabien Pinckaers)

   • Data are stored in the database in UTC (not depending on the timezone of your users)

     When the client receives the data, it translates it according to the timezone of the user which is on the global context that comes from the user preferences (so, the date/time you see on the screen is not the same than the one in the database)

     The client sends back the new dates to the server under the UTC format

2. Read also this https://github.com/WillowIT/Pentaho-reports-for-OpenERP/wiki/Some-Notes-about-Dates-and-Datetimes

3. Known also that OpenERP relies on the following python libraries to handle all the Time, Date and calendar Data.

   Python Time - https://docs.python.org/2.7/library/time.html#module-time

   Python datetime - https://docs.python.org/2/library/datetime.html#module-datetime

   Python Calendar – https://docs.python.org/2.7/library/calendar.html?highlight=calendar#module-calendar

   Unfortunately, all this work was done based on the Gregorian calendar.

And this is also the case for Postgresql: the 'datetime values' are constrained by the natural rules for dates and times according to the Gregorian calendar ( taken from http://www.postgresql.org/docs/current/static/datetime-units-history.html)

1. At the web side OpenERP use the following libraries: Javascrip dates used for parsing, formatting and processing - * jquery-ui-timepicker-addon* used to add a datetimepicker, datepicker or timepicker dropdown …

Where to begin ?

Lost between Python, Javascript, and Postgresql.

But, Time, Date and Calendar works fine in OpenERP (for the Gregorian sytem) !

The first idea that comes to me is, to just use Two functions in one single JS file, for converting from and to Gregorian calendar :

-The first, for converting from Gregorian to Hijri (or to any other calendar system) after reading data from DB and just before returning the result, to the calling function.

• The second, for converting from Hijri to Gregorian, Just before returning the data for writing into the DB.

  And let OpenERP Web doing his Job as before.

This way, we don't have to overwrite any files, but just inserting 2 calls to the related functions ( for example in dates.js). (No need to reinvent the wheel).

Is this enough ?

Certainly, not.

The next step, is to deal with the datetimepicker , and the hidden things …

Personnaly i've tried with 3 JS files:

https://github.com/xsoh/Hijri.js/blob/master/Hijri.js

https://github.com/talomaireeni/Umm-Al-Qura-Calendar/blob/master/UQCal.js

and http://www.al-habib.info/islamic-calendar/hijricalendartext.htm

and i can't get a suitable result, except the correct conversion of the current date field.

This is certainly due to my lack of mastery of Javascript, the lack of the OpenERP technical documentation, and the time reserved for this task.

Tired of reading all the Firebug error messages, and the JS code, tired of reading between the lines of python code to see how things are done, to try to understand what's going on, and what's wrong.

So tired, that i've decided to stop working, and take a rest for some moments, take a cofee and browse the web ...

Browsing the web, with the help of my favorite search engine, and as if by chance i came across this link:

jQuery Calendars

A wonderful thing.

This is an Open Question: Everyone interested by this subject should contribute not only by giving an answer, but above all by contributing to the question itself.

A way to show that the subject of the question is of great importance for many of OpenERP users.

And why not, making the solution to this question a part of the OpenERP Web.

The next steps ...

Giving the Responses ...

Building the Solution ... With the help of jQuery Calendars

To be continued ...