Hi,

Tracking is used to record each and every action or update of a particular field.

For example:

from odoo import models, fields

class SaleOrder(models.Model):
    _inherit = 'sale.order'

    expected_date = fields.Datetime(
        string="Expected Date",
        compute='_compute_expected_date',
        store=False,
        tracking=True,
        help="Delivery date you can promise to the customer, computed from the minimum lead time of the order lines."
    )

A log will be recorded with from and to values when the value of expected_date is changed.

If you want a custom log note (like posting a message in the chatter when the date changes), you can either:

1. Override the existing compute function (if appropriate), or
2. Create a custom write method to detect and log the change.
   
   Example Code:

class SaleOrder(models.Model):

    _inherit ='sale.order'

def _compute_expected_date(self):

       res = super()._compute_expected_date()

        self.message_post(body=_("The delivery date has changed the new date is - %s", res)

          return res

This will ensure that whenever the delivery/commitment date (expected_date) is changed, the new date will be posted in the chatter.

Hope it helps