Jinja2 Documentation and Custom Filters Guide

Introduction to Jinja2

Jinja2 is a modern and designer-friendly templating language for Python, modeled after Django’s templates. It is fast, widely used, and secure with the optional sandboxed template execution environment.

Official Documentation

For comprehensive details, you can refer to the official Jinja2 documentation:

Jinja2 Documentation

Timezones

Filters that render a timestamp (datetime, date) interpret it as UTC by
default. This is unchanged behaviour and applies to every existing template.

To render in a local timezone, pass the optional tz argument with an
IANA timezone name
such as Europe/Paris or Asia/Seoul. Daylight saving time is handled
automatically, per timestamp — a slot in July renders at UTC+02:00 and a slot in
December at UTC+01:00 without any work in the template.

Pass tz wherever you format, not only where you format the hour. Converting to
a local timezone can move the date as well as the time, so the day name (%w,
%A), day number (%d) and full date (%Y-%m-%d) all change:

{{ 1787092200 | datetime('%Y-%m-%d %H:%M') }}
{{ 1787092200 | datetime('%Y-%m-%d %H:%M', tz='Europe/Paris') }}

Output:
2026-08-18 22:30
2026-08-19 00:30

If tz is omitted the timestamp is rendered in UTC. If tz is not a recognised
timezone name, the filter falls back to UTC rather than failing the template.

Custom Filters

For more advanced data management and date manipulation, Alcmeon already implemented the following custom filters.

parse_iso_date

Can be applied on an ISO date and return a Python datetime object.
Supports any format that is allowed by Python datetime.fromisoformat() function. See Documentation

date = '2011-11-04T00:05:23Z' | parse_iso_date

date_now

No input required. Return the date of the execution as a Python datetime object.

now = '' | date_now

add_days

Must be applied on a Python datetime and need a number of days to add. Works with negative number of days if you want to substract days.

updated_date = date | add_days(4)   # Add 4 days to the variable 'date'

add_hours

Must be applied on a Python datetime and need a number of hours to add. Works with negative number of hours if you want to substract hours.

updated_date = date | add_hours(4)   # Add 4 hours to the variable 'date'

add_minutes

Must be applied on a Python datetime and need a number of minutes to add. Works with negative number of minutes if you want to substract minutes.

updated_date = date | add_minutes(4)   # Add 4 minutes to the variable 'date'

datetime

Formats a timestamp to a readable date and time string.
Takes an optional format input. Default format is %Y-%m-%d @ %H:%M.
Takes an optional tz argument (IANA timezone name). Defaults to UTC.

"1745392360" | datetime
"1745392360" | datetime("%Y-%m-%d %H:%M:%S")
"1745392360" | datetime("%Y-%m-%d %H:%M", tz="Europe/Paris")
"1735732800" | datetime("%Y-%m-%d %H:%M", tz="Europe/Paris")
"1745392360" | datetime("%Y-%m-%d %H:%M %z", tz="Europe/Paris")

Output:
2025-04-23 @ 07:12
2025-04-23 07:12:40
2025-04-23 09:12
2025-01-01 13:00
2025-04-23 09:12 +0200

date

Formats a timestamp to a readable date string.
Takes an optional format input. Default format is %Y-%m-%d.
Takes an optional tz argument (IANA timezone name). Defaults to UTC.

"1745392360" | date
"1745392360" | date("%Y %m %d")
"1787092200" | date(tz="Europe/Paris")

Output:
2025-04-23
2025 04 23
2026-08-19

ddatetime

Formats a Python datetime object to a readable date and time string.
Takes an optional format input. Default format is %Y-%m-%d @ %H:%M.

 datetime_obj | ddatetime
 datetime_obj | ddatetime("%Y-%m-%d %H:%M:%s")

Output:
2025-04-23 @ 07:12
2025-04-23 07:12:40

ddate

Formats a Python datetime object to a readable date string.
Takes an optional format input. Default format is %Y-%m-%d.

 datetime_obj | ddate
 datetime_obj" | ddate("%Y %m %d")

Output:
2025-04-23
2025 04 23

to_datetime

Converts a timestamp into a Python datetime object (in UTC), so that
timestamps can be used with the datetime-object filters (in_tz, add_days,
add_hours, add_minutes, ddatetime, ddate).

slot = "1745392360" | to_datetime

in_tz

Must be applied on a Python datetime. Converts it to the given timezone,
keeping the same instant in time.
Requires an IANA timezone name. Falls back to UTC if the name is not
recognised.
Use this instead of the tz argument when you format the same value several
times: convert once, then format as often as you need.

{% set slot = "1787092200" | to_datetime | in_tz("Europe/Paris") %} {{ slot | ddate }} at {{ slot | ddatetime("%Hh%M") }}

Output: 2026-08-19 at 00h30

datetime_diff

Calculates the difference between the current datetime and a given timestamp, returning a tuple with the unit and value.

 "1745392360" | datetime_diff

Output one of:
('s', 30) -> 30 seconds of difference
('m', 12) -> 12 minutes of difference
('h', 3) -> 3 hours of difference
('d', 14) -> 14 days of difference
If the difference is less than 1 minute, it is displayed in seconds. If the difference is between 1 minute and 1 hour, it is displayed in minutes. For differences between 1 hour and 1 day, it is displayed in hours. For differences greater than 1 day, it is displayed in days.

datetime_diff

Calculates the difference in days between the current date and a given timestamp.

 "1745392360" | datetime_diff

Output one of:
1 <= 1 day difference
14 14 days of difference

addslashes

Escapes special characters in a string.

"Hello\nWorld" | addslashes

Output: Hello\\nWorld

domain_from_url

Extracts the domain from a URL.

"https://www.example.com/path" | domain_from_url

Output: www.example.com

render_links

Converts URLs in a string to clickable HTML links.

"Visit https://www.example.com for more info." | render_links

Output: Visit <a href="https://www.example.com" target="_blank">https://www.example.com</a> for more info.

json_escape

Escapes special characters for use in JSON strings.

"{"key": "v/al'ue"}" | json_escape

Output: {\"key\": \"v\/al\'ue\"}

escape_url

URL-encodes a string.

"Hello World" | escape_url

Output: Hello+World

str

Converts a number to a string.

{{ 10 | str }}

Output: "10"

to_int

Converts a string to a number.

 {{ "10" | str }}

Output: 10

lower

Converts a string to lowercase.

 {{ "ABC" | lower }}

Output: abc

set_exit

Allows to set an exit node in the Code box. Can only be used in this context. Check this documentation for more details

{{ set_exit("exit_ref" }}

Output: Nothing, only set an exit.

log

Allows to log data in the Code box. Can only be used in this context. Check this documentation for more details

{{ log("Test" }}

Output: Nothing, only store log in debug context.