esphome/tests/integration/fixtures/template_time.yaml

esphome:
  name: template-time-test
host:
api:
logger:

time:
  - platform: template
    id: fixed_time
    lambda: |-
      return 1700000000;

  # Derived from another time source, as when offsetting a real clock.
  - platform: template
    id: offset_time
    lambda: |-
      return id(fixed_time).timestamp_now() + 3600;

  # A lambda that gives no value reports an invalid time.
  - platform: template
    id: empty_time
    lambda: |-
      return {};

text_sensor:
  # Timestamps are exposed as text (rather than a 32-bit float sensor state,
  # which cannot represent a UNIX epoch exactly) so the exact value can be checked.
  - platform: template
    name: "Fixed Timestamp"
    id: fixed_timestamp
    update_interval: 100ms
    lambda: |-
      return std::to_string(id(fixed_time).now().timestamp);

  - platform: template
    name: "Offset Timestamp"
    id: offset_timestamp
    update_interval: 100ms
    lambda: |-
      return std::to_string(id(offset_time).now().timestamp);

  - platform: template
    name: "Empty Time Valid"
    id: empty_time_valid
    update_interval: 100ms
    lambda: |-
      return std::string(id(empty_time).now().is_valid() ? "valid" : "invalid");