Time component¶

Every Field carries a time component that describes the temporal coordinate of the field. The time component is accessible via the time attribute of a field and is represented by a subclass of TimeBase.

>>> import earthkit.data as ekd
>>> field = ekd.from_source("sample", "test.grib").to_fieldlist()[0]
>>> field.time.base_datetime()
datetime.datetime(2020, 1, 1, 0, 0)
>>> field.time.step()
datetime.timedelta(0)
>>> field.time.valid_datetime()
datetime.datetime(2020, 1, 1, 0, 0)

The same information is available through the generic get() interface using the "time." prefix:

>>> field.get("time.base_datetime")
datetime.datetime(2020, 1, 1, 0, 0)
>>> field.get("time.step")
datetime.timedelta(0)

The time component is immutable. Use the set() method (or set() on the field) to derive a modified copy:

>>> new_field = field.set({"time.step": 6})
>>> new_field.time.step()
datetime.timedelta(seconds=21600)

Time types¶

The appropriate time subclass is determined automatically from the data:

ForecastTime — standard forecast time defined by a base datetime and a forecast step. The valid datetime is computed as base_datetime + step.
MonthlyForecastTime — monthly forecast time that also carries a forecast_month value.

Accessing time information¶

All time keys are accessible through get() with the "time." prefix, and can therefore be used in sel(), order_by(), and metadata().

Key	Description
`time.base_datetime`	The base (reference) datetime of the forecast as a `datetime.datetime`.
`time.forecast_reference_time`	Alias of `time.base_datetime`.
`time.base_date`	The date part of the base datetime as a `datetime.date`.
`time.base_time`	The time-of-day part of the base datetime as a `datetime.time`.
`time.valid_datetime`	The valid datetime (`base_datetime + step`) as a `datetime.datetime`.
`time.step`	The forecast step as a `datetime.timedelta`. Integer values are interpreted as hours.
`time.forecast_period`	Alias of `time.step`.
`time.forecast_month`	The forecast month as an integer. Only available for monthly forecast time; returns `None` otherwise.
`time.indexing_datetime`	The indexing datetime used for ordering within a dataset. Returns `None` for types that do not define it.

How-tos¶