# xarray.coders.CFDatetimeCoder

### *class* xarray.coders.CFDatetimeCoder(use_cftime=None, time_unit='ns', infer_dtype='data')[[source]](https://github.com/pydata/xarray/blob/main/xarray/coding/times.py#L1420-L1540)

Coder for CF Datetime coding.

* **Parameters:**
  * **use_cftime** ([`bool`](https://docs.python.org/3/builtins/functions.html#bool), *optional*) – Only relevant if encoded dates come from a standard calendar
    (e.g. “gregorian”, “proleptic_gregorian”, “standard”, or not
    specified).  If None (default), attempt to decode times to
    `np.datetime64` objects; if this is not possible, decode times to
    `cftime.datetime` objects. If True, always decode times to
    `cftime.datetime` objects, regardless of whether or not they can be
    represented using `np.datetime64` objects.  If False, always
    decode times to `np.datetime64` objects; if this is not possible
    raise an error.
    May not be supported by all the backends.
  * **time_unit** (`PDDatetimeUnitOptions`) – Target resolution when decoding dates. Defaults to “ns”.
  * **infer_dtype** (`{"data", "metadata"}`, *default*: `"data"`) – How to infer the dtype of the decoded variable:
    - `"data"` (default): read the first and last values from the
      store to verify they decode successfully. Preserves
      backwards-compatible behavior, including the auto-fallback to
      `cftime.datetime` for values outside the
      `np.datetime64[ns]` range.
    - `"metadata"`: infer the dtype from `units`, `calendar`,
      `use_cftime` and `time_unit` alone, assuming the stored dates
      lie near the reference date in `units`. Nothing is read from
      the store, which speeds up opening remote stores with many
      time-encoded variables. The first and last values are read, as
      with `"data"`, only when metadata cannot tell: when, with
      `use_cftime=None` and a standard calendar, dates near the
      reference date need `cftime` (e.g. `"hours since 1-1-1"` or a
      reference date before 1582-10-15), or when decoding dates near
      the reference date fails.

      The stored values are checked when they are decoded instead, and a
      `ValueError` is raised then if they need a different dtype than
      inferred. This happens for dates outside the
      `np.datetime64[time_unit]` range (pass `use_cftime=True` or a
      coarser `time_unit` such as `"s"`) and for floating point
      values with fractions finer than `units`, e.g. `0.5` with
      `"seconds since ..."` (pass a `time_unit` fine enough to
      represent them). Index coordinates are decoded when the dataset
      is opened, other variables when they are loaded.

#### \_\_init_\_(use_cftime=None, time_unit='ns', infer_dtype='data')[[source]](https://github.com/pydata/xarray/blob/main/xarray/coding/times.py#L1468-L1480)

### Methods

| [`__init__`](#xarray.coders.CFDatetimeCoder.__init__)([use_cftime, time_unit, infer_dtype])   |                                                    |
|---------------------------------------------------------------------------------------------------|----------------------------------------------------|
| `decode`(variable[, name])                                                                        | Convert a decoded variable to an encoded variable. |
| `encode`(variable[, name])                                                                        | Convert an encoded variable to a decoded variable. |