> ## Documentation Index
> Fetch the complete documentation index at: https://nixtlaverse.nixtla.io/llms.txt
> Use this file to discover all available pages before exploring further.

# Custom date features

> Define your own functions to be used as date features

```python theme={null}
from mlforecast import MLForecast
from mlforecast.utils import generate_daily_series
```

The `date_features` argument of MLForecast can take pandas date
attributes as well as functions that take a [pandas
DatetimeIndex](https://pandas.pydata.org/docs/reference/api/pandas.DatetimeIndex.html)
and return a numeric value. The name of the function is used as the name
of the feature, so please use unique and descriptive names.

```python theme={null}
series = generate_daily_series(1, min_length=6, max_length=6)
```

```python theme={null}
def even_day(dates):
    """Day of month is even"""
    return dates.day % 2 == 0

def month_start_or_end(dates):
    """Date is month start or month end"""
    return dates.is_month_start | dates.is_month_end

def is_monday(dates):
    """Date is monday"""
    return dates.dayofweek == 0
```

```python theme={null}
fcst = MLForecast(
    [],
    freq='D',
    date_features=['dayofweek', 'dayofyear', even_day, month_start_or_end, is_monday]
)
fcst.preprocess(series)
```

|   | unique\_id | ds         | y        | dayofweek | dayofyear | even\_day | month\_start\_or\_end | is\_monday |
| - | ---------- | ---------- | -------- | --------- | --------- | --------- | --------------------- | ---------- |
| 0 | id\_0      | 2000-01-01 | 0.274407 | 5         | 1         | False     | True                  | False      |
| 1 | id\_0      | 2000-01-02 | 1.357595 | 6         | 2         | True      | False                 | False      |
| 2 | id\_0      | 2000-01-03 | 2.301382 | 0         | 3         | False     | False                 | True       |
| 3 | id\_0      | 2000-01-04 | 3.272442 | 1         | 4         | True      | False                 | False      |
| 4 | id\_0      | 2000-01-05 | 4.211827 | 2         | 5         | False     | False                 | False      |
| 5 | id\_0      | 2000-01-06 | 5.322947 | 3         | 6         | True      | False                 | False      |