There is the email_template_dateutil module in OCA/server-tools:

https://github.com/OCA/server-tools/tree/7.0/email_template_dateutil

This module adds the format_date filter in the email template environment, and can be used like this:

${object.date_invoice|format_date("%m/%d/%Y")}

${object.some_datetime|format_date()}

This will use the current user's timezone by default, or the server timezone, or you can pass in your own timezone.

SIMPLE:

We Know the date format output by: ${object.date_invoice} (or any other date) in Email Templates is: YYYY-MM-DD.

We also know that Python sees the value as a string. Use the built in split() method to output each part of the date like so:

For DD-MM-YYYY formatted date:

Replace: ${object.date_invoice}

With: ${object.date_invoice.split('-')[2] + '-' + object.date_invoice.split('-')[1] + '-' + object.date_invoice.split('-')[0]}

No extending classes or writing custom modules!!

I like it though... In my case Format was YYYY-MM-DD hh:mm:ss Just wanted DD-MM-YYYY So ${(object.date.split('-')[2]).split(' ')[0] + '-' + object.date.split('-')[1] + '-' + object.date.split('-')[0]}

This worked for me in V13

${format_datetime(object.date_from, tz=object.employee_id.tz, dt_format='dd.MM.YYYY')}

You can find more details on the template language at http://jinja.pocoo.org/docs/dev/templates/#builtin-filters

I opened a bug about this on github:

https://github.com/odoo/odoo/issues/1108

Oke, can you give an example of extending an object by a openerp module?

Because I would really like, to follow the correct way.

Only editing the template is not possible to fix this. Not only the format is wrong even the timezone is alway UTC and this is confusing if your are outside UTC.

A workaround is to defined a new field as function:

    def _get_date_for_email(self, cr, uid, ids, field_name, arg, context=None):
        reads = self.browse(cr, uid, ids, context)   
        result = {}     
        for obj in reads:        
            utc = datetime.strptime(obj.date, '%Y-%m-%d %H:%M:%S').replace(tzinfo=pytz.timezone('UTC'))
            #FIXME: can we read timezone from context?            
            #if 'tz' in context:            
            #    to_zone = tz.gettz(context['tz'])
            #else:
            to_zone = tz.gettz('Europe/Berlin')
            meeting_date = utc.astimezone(to_zone)
            #TODO: Make formating here
            result[obj.id] = "%s" % meeting_date
        return result

    _columns = {
        'date_for_email' : fields.function(
            _get_date_for_email,
            type='char',
            readonly=True,
            string='Date Formated'),
    }

Maybe we need a more generic solution of this. The OpenERP Support offer me to develop a private patch but not merging to stable. I think a small community module should be the best way. So we will work on this.