Update templating.markdown for as_datetime (#39498)

TheFes · web-flow · commit 43db9e66b1aa · 2025-06-12T14:42:18.000+02:00
diff --git a/source/_docs/configuration/templating.markdown b/source/_docs/configuration/templating.markdown
@@ -774,7 +774,7 @@ For example, if you wanted to select a field from `trigger` in an automation bas
 
   {% endraw %}
 
-- `as_datetime(value, default)` converts a string containing a timestamp, or valid UNIX timestamp, to a datetime object. If that fails, it returns the `default` value or, if omitted, raises an error. When the input is already a datetime object it will be returned as is. in case the input is a datetime.date object, midnight will be added as time. This function can also be used as a filter.
+- `as_datetime(value, default)` converts a string containing a timestamp or a valid UNIX timestamp to a datetime object. If conversion fails, the function returns the `default` value. If no `default` is provided and the input is a string that cannot be converted to a datetime, it returns `None`. For other invalid inputs (e.g., a list, dictionary, or a numeric value too large to convert), it raises an error when no `default` is supplied. In case the input is already a datetime object, it is returned unchanged. If the input is a `datetime.date` object, midnight is added as the time. This function can also be used as a filter.
 - `as_timestamp(value, default)` converts a datetime object or string to UNIX timestamp. If that fails, returns the `default` value, or if omitted raises an error. This function can also be used as a filter.
 - `as_local()` converts a datetime object to local time. This function can also be used as a filter.
 - `strptime(string, format, default)` parses a string based on a [format](https://docs.python.org/3/library/datetime.html#strftime-and-strptime-behavior) and returns a datetime object. If that fails, it returns the `default` value or, if omitted, raises an error.
