<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def value(self, new_value):
 """ Updates the value. If the change exceeds the change delta observers and linked values are notified. """

        datetime_value = None
        if new_value:
            datetime_value = new_value.strftime("%Y-%M-%dT%H:%M:%SZ")
        self._set_value(datetime_value)