example.yaml

esphome:
  name: system-time

esp32:
  board: esp32dev
  framework:
    type: arduino

external_components:
  - source: components

wifi:
  networks:
    - ssid: !secret wifi_ssid
      password: !secret wifi_password
api:

ota:
  - platform: esphome
    password: !secret ota_password

logger:
  baud_rate: 0

web_server:

time:
  - platform: system_time
    id: sys_time
    start_datetime:
      year: 2024
      month: 12
      day: 31
      hour: 12
      minute: 34
      second: 56
    on_time:
      - seconds: /5
        then:
          lambda: |-
            ESP_LOGD("", "it's %s", id(sys_time).now().strftime("%Y-%m-%d %H:%M:%S").c_str());

datetime:
  - platform: template
    id: start_datetime
    type: datetime
    name: Pick a start datetime
    optimistic: yes
    on_value:
      then:
        system_time.start_datetime_set: !lambda 'return x;'

  - platform: template
    id: current_datetime
    type: datetime
    name: Pick a current datetime
    optimistic: yes
    on_value:
      then:
        - system_time.current_datetime_set: !lambda 'return x;'