Test if datetime: datetime

The datetime test checks whether a value is a datetime object, a specific moment in time with a date and a time. It returns true for datetime objects and false for everything else, including date-and-time strings, UNIX timestamps, and date-only values.

Many sensors and attributes provide dates and times as plain text or numbers. This test lets you check whether a value is already a datetime before you compare it, calculate with it, or convert it with as_datetime.

Usage

Here’s how to use this template function. Copy any example and adjust it to your setup.

{% if now() is datetime %}
  It is a datetime
{% endif %}

It is a datetime

Function signature

The signature is a technical summary of this template function. It shows the name of the function, the values (called parameters) it accepts, and what type of data each parameter expects (for example, a piece of text or a number).

Function parameters that have a = with a value after them are optional. If you leave them out, the default value shown is used automatically.

Function parameters without a = are usually required. A few optional parameters have no default value, so the signature shows them without a = as well. To check whether a parameter is required, look at the parameter list below the signature. Each parameter is marked as Required or Optional.

The most common optional parameter without a default value is default. The default parameter sets the value a function returns when the function can’t produce a result, for example, when float gets text that isn’t a number. If you leave out default, there is no fallback value, so most functions raise an error and the template fails. The parameter list of each function says what happens. If you set default, the function returns your value instead.

round(
    value: Any,
    precision: int = 0,
    method: str = "common",
    default: Any,
) -> float | int | Any

datetime(
    value: Any,
) -> bool

Function parameters

The following parameters can be provided to this test.

Good to know

• Only real datetime objects pass. Strings like "2024-03-15T14:30:00+01:00", UNIX timestamps, and date-only values do not.
• Datetimes with and without a time zone both pass.
• To convert a string or a UNIX timestamp, use as_datetime. It returns None for invalid text, and None does not pass this test.

Try it yourself

Ready to test this? Open Settings > Tools > Template, paste the example into the Template editor, and watch the result update on the right. Edit the values to see how the function adapts to your own entitiesAn entity represents a sensor, actor, or function in Home Assistant. Entities are used to monitor physical properties or to control other entities. An entity is usually part of a device or a service. [Learn more].

More examples

Real scenarios where this function comes up in automations and templates. Copy any example and adapt it to your setup.

Distinguish a datetime from other values

Check whether a value is a datetime rather than a string or a number.

{{ now() is datetime }}
{{ "2024-03-15T14:30:00+01:00" is datetime }}
{{ as_datetime("2024-03-15T14:30:00+01:00") is datetime }}
{{ 1710510600 is datetime }}

true
false
true
false

Convert to a datetime only when needed

Convert a value with as_datetime only if it is not already a datetime.

{% set value = "2024-03-15T14:30:00+01:00" %}
{% set moment = value if value is datetime else as_datetime(value) %}
{{ moment }}

2024-03-15 14:30:00+01:00

Check that a conversion worked

as_datetime returns None for text it cannot parse, so test the result before you use it.

{% set moment = as_datetime("not a date") %}
{% if moment is datetime %}
  Year: {{ moment.year }}
{% else %}
  Not a valid date
{% endif %}

Not a valid date

Still stuck?

The Home Assistant community is quick to help: join Discord for real-time chat, post on the community forum with your template and expected result, or share on our subreddit /r/homeassistant.

Related template functions

These functions work well alongside this one:

• Convert to datetime: as_datetime - Converts a string or timestamp to a datetime object.

• Convert to local time zone: as_local - Converts a datetime object to your local time zone.

• Current local date and time: now - Returns the current date and time in your local time zone.

• Get the type of a value: typeof - Returns the type name of a value as a string.