Adjust date and time
=============================

.. note::
   
    The Macro to Python converter is available from Metview version 5.22.0

Date/time literals and dates initialised from numbers in Macro are automatically converted to Python datetime objects:

.. list-table:: Date/time literals converted to Python
   :header-rows: 1
 
   * - Macro code
     - Generated Python code
   * -
       .. code-block:: python
            
        d = 2019-03-21      
        t = 03:11:32      
        d1 = 2021-03-21 05:11:32
        d2 = date(20220321)
     -
       .. code-block:: python

        d = datetime.date(2019, 3, 21)  
        t = datetime.time(3, 11, 32) 
        d1 = datetime.datetime(2021, 3, 21, 5, 11, 32) 
        d2 = mv.date(20220321)

        
However, a problem arises when it comes down to date arithmetics. In Macro we can add floating point numbers to a date (1=1 day, 0.5=12 hours etc). However, in Python only a **datetime.timedelta** object can be added to a date. The converter is not able to resolve this, therefore every occurrence has to be **checked and manually adjusted** in the generated Python code. This is true for cases when:

- we directly add a number to a date
- we add the result of the ``year()``, ``month()``, ``day()``, ``hour()``, ``minute()`` or ``second()`` Macro functions to a date (see function reference :ref:`here <macro_date_fn>`)
- we add a number stored in a variable or generated by an expression to a date

The following examples demonstrate how the adjustment can be done in various use cases:

.. list-table:: Adding days to a date
   :header-rows: 1
 
   * - Macro
     - Generated Python code
     - Adjusted Python code
   * -
       .. code-block:: python
            
        d = 2019-03-21  
        # add 1 day    
        d1 = d + 1      
     -
       .. code-block:: python

        d = datetime.date(2019, 3, 21) 
        # not supported in datetime
        d1 = d + 1

     -
       .. code-block:: python

        d = datetime.date(2019, 3, 21) 
        # correct 
        d1 = d + datetime.timedelta(days=1)

.. list-table:: Adding fractional days to a date
   :header-rows: 1
 
   * - Macro
     - Generated Python code
     - Adjusted Python code
   * -
       .. code-block:: python
            
        d = 2019-03-21  
        # add 1.5 day    
        d1 = d + 1.5     
     -
       .. code-block:: python

        d = datetime.date(2019, 3, 21) 
        # error: not supported in datetime
        d1 = d + 1.5

     -
       .. code-block:: python

        d = datetime.date(2019, 3, 21) 
        # correct 
        d1 = d + datetime.timedelta(days=1, hours=12)

.. list-table:: Adding hours to a date
   :header-rows: 1
 
   * - Macro
     - Generated Python code
     - Adjusted Python code
   * -
       .. code-block:: python
            
        d = 2019-03-21  
        # add 1 hours    
        d1 = d + hour(1)      
     -
       .. code-block:: python

        d = datetime.date(2019, 3, 21) 
        # error: not supported in datetime
        d1 = d + mv.hour(1)

     -
       .. code-block:: python

        d = datetime.date(2019, 3, 21) 
        # correct 
        d1 = d + datetime.timedelta(hours=1)