RESTful sensors + Battery State Card question

Configuration
1

I want to display my backups in my dashboard, or rather, whether they are overdue and when they were last created. I’m not referring to backups from Home Assistant itself, but rather backups created by other computers or smartphones. Whenever a backup is created on my end, the status is recorded in a JSON file. I can retrieve this via an HTTP request, which usually tells me which device created the last backup. In the same JSON file, it also states how many days the backup is required for this type. I have now created a sensor in HA using the RESTful integration that converts the response into entities. The JSON looks something like this (+ additional types):

{
    "bbackup": {
        "name": "Backup",
        "days": "30",
        "last": "01 Apr 2026 12:17:27"
    },
    "calibre": {
        "name": "Calibre",
        "days": "3",
        "last": "01 Apr 2026 20:36:27"
    }
}

Since I’ve been experimenting with the Battery State Card lately, I’d like to use the same integration to show whether a backup is overdue. In the bbackup example, the last backup was on April 1, 2026, at 12:17:27 PM; it’s supposed to be created every 30 days, so it’s not due yet. This should be displayed in green. The Calibre backup is from “April 1, 2026, 8:36:27 PM,” but it’s supposed to be created every 3 days, so it’s overdue and should be displayed in red. The backups themselves usually start automatically and on time. However, sometimes the rsync server is unavailable or the source device has been offline for an extended period; in such cases, the backup cannot start and may become overdue.

I have used the following in configuration.yaml to integrate the sensor:

rest:
  - authentication: basic
    username: "myuser"
    password: "mypassword"
    scan_interval: 43200
    resource: https://mydomain.com/?action=getbackups
    method: GET
    headers:
      Accept: application/json
    sensor:
      - name: "bbackup"
        unique_id: 22c32b5b-8c0c-4995-8a38-2838f78ac147
        json_attributes_path: "$.bbackup"
        device_class: timestamp
        value_template: "{{ as_timestamp(strptime(value_json.bbackup.last, '%d %b %Y %H:%M:%S')) | timestamp_local }}"
        json_attributes:
          - "last"
          - "name"
          - "days"
      - name: "calibre"
        json_attributes_path: "$.calibre"
        unique_id: e30614af-4a31-4ffa-a3d8-f911bbd0ece2
        device_class: timestamp
        value_template: "{{ as_timestamp(strptime(value_json.calibre.last, '%d %b %Y %H:%M:%S')) | timestamp_local }}"
        json_attributes:
          - "last"
          - "name"
          - "days"

The JSON attributes are read correctly, and I can retrieve them in the entity. But how can I create an “Overdue” attribute from this and use it as a threshold in the Battery State Card?

My card looks like the following:

type: custom:battery-state-card
title: Backups
secondary_info: In {attributes.days} Days
icon: null
entities:
  - entity: sensor.bbackup
  - entity: sensor.calibre
sort: name

I know, i can use something like

colors:
  steps:
    - value: 0
      color: green
    - value: 1
      color: red

to specify colors for the tresholds. I know if i calculate "days" / ("now" - "last") i get either smaller zero (overdue/red) or bigger/equal zero (in time/green). But i don’t know, how to use this to decide if the entry is green or red.
Can someone please take me in the right direction?

2

It seems, i have found a way. I have now changed value_template in configuration.yaml to:

value_template: "{{ (value_json.bbackup.days | int) - ((today_at() - (as_timestamp(strptime(value_json.bbackup.last, '%d %b %Y %H:%M:%S')) | timestamp_local) | as_datetime).days | int) | int }}"

This calculates a state where states between 0 and higher are interpreted as “in-time” and all smaller as 0 is “overdue”.

The card looks now like:

type: custom:battery-state-card
style: |
  .state {
    display: none;
  }
title: Backups
secondary_info: "{attributes.last}"
icon: mdi:backup-restore
entities:
  - entity: sensor.bbackup
  - entity: sensor.calibre
colors:
  steps:
    - value: 0
      color: red
    - value: 1
      color: orange
    - value: 2
      color: lime
sort:
  - state
  - name

I hide the state with a custom style. In the color definition i set all red what is below 0 and green what is higher. 1 is orange for backups of today. Maybe there are better options, but it seems, that this comes a little bit closer, to what i want.