Control datetime

datetime control

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Minimal field JSON:

{
  "id": "datetime",
  "type": "datetime",
  "name": "Datetime"
}

Full field JSON:

{
  "id": "datetime",
  "type": "datetime",
  "name": "Datetime",
  "default": "2000-01-01T00:00:00Z",
  "controls": [
    {
      "key": "",
      "type": "datetime",
      "label": "ui_049",
      "command": ""
    }
  ],
  "ha": {
    "state_topic": "$state",
    "command_topic": "$command"
  }
}

Properties in the full example:

Property	Required?	Meaning / default
id	Required	Stable application key; unique across registered pages.
type	Required	Enabled field type.
name	Required title¹	Display title; may be replaced by a nonempty names object.
default	Optional	Omit to use the built-in initial value.
controls	Optional	Omit to use the preset controls; supplying an array replaces them.
ha	Optional	Omit to use automatic HA discovery; supplied properties override defaults.

¹ name can be replaced by names. Other shared optional properties are listed in the catalogue.

Default / example: "2000-01-01T00:00:00Z"

Date/time input with an ISO-style string containing a timezone: for example 2026-10-02T12:30:00Z or 2026-10-02T14:30:00+02:00. Fractional seconds are accepted. The browser control sends a UTC Z value.

Integration with Home Assistant

MQTT component: datetime. Requires the control’s feature flag, dynamic pages, MQTT and HA support to be enabled. ArdPortal registers MQTT Discovery and routes state/commands; the sketch implements device behavior. Action callbacks acknowledge acceptance, not physical completion.

Supported by ArdPortal: Read/write timestamp state and commands with a calendar date, time and explicit Z or UTC offset. The validator accepts optional fractional seconds (up to six digits).

Not provided by the built-in integration / limits: No timezone database, recurring schedule, automatic clock-setting or conversion of the stored timestamp. The application owns interpretation and execution.

Explicit ha properties can override Discovery metadata. They do not create additional hardware behavior, application value properties or command handlers by themselves. See HA integration for the shared setup.

Integration with Zigbee

Status: not mapped by ArdPortal. Timestamp values and commands are not mapped; there is no automatic Zigbee Time endpoint. Enabling Zigbee does not create an endpoint for this field. The field remains usable in the portal and through MQTT/HA when those features are enabled.

This describes the current ArdPortal implementation, not a claim that Zigbee cannot represent a similar device through a standard cluster or a gateway-specific converter.

Possible extension, not implemented: Time cluster for the device clock; custom UTC-time attribute for an application timestamp. The Time cluster can exchange actual device/network clock information. Independent AppConfig timestamps need their own attributes and a converter. ZCL UTC time has a fixed epoch/range and does not preserve the original offset or fractional-second representation. It cannot reproduce every accepted ArdPortal timestamp unchanged. See the mapping feasibility table.

See Zigbee integration for pairing, endpoint lifecycle, gateway limitations and OTA requirements.

Read and update values from C++

These examples use the field ID from the JSON above and an existing ArdPortal portal. Run them after page registration has finished and portal.portalAndAppConfigReady() is true. Call portal.loop() frequently. Register callbacks once in setup(); do not repeat setters on every loop iteration.

Set the value with automatic ArdFS persistence

Set "persist": true on this field in its page JSON. It is optional for editable fields whose preset already persists settings, but required to override a RAM-only preset such as a sensor. Calling setAppConfigValue() sets the control value and ArdPortal automatically saves AppConfig through its integrated ArdFS storage. Do not create an ArdFS object or call a separate write/flush method. The automatic save is coalesced and advanced by subsequent portal.loop() calls.

// Use this path when the value is a setting that should survive restart.
ArdJSON::JSONVar next = "2000-01-01T00:00:00Z";
if (!next.isValid() || !portal.setAppConfigValue("datetime", next)) {
  Serial.println("Setting rejected or storage temporarily unavailable");
}

true from the setter means acceptance, not a completed flash write. Configure this callback once to observe the result:

portal.onPortalAndAppConfigSaved([](bool ok, const String& error) {
  if (!ok) Serial.println(error);
});

Update only RAM

// Use this alternative for live readings/status; never writes ArdFS.
ArdJSON::JSONVar next = "2000-01-01T00:00:00Z";
if (!next.isValid() || !portal.setAppConfigStateValue("datetime", next, false)) {
  Serial.println("Runtime value rejected");
}

The third argument false avoids queuing an immediate MQTT publication. Use true or omit it to queue changed state. RAM updates work regardless of persist. Alternatively, with "persist": false, setAppConfigValue() also follows the RAM-only path.

Read the current value

const ArdJSON::JSONVar current = portal.getAppConfigValue("datetime");
if (!current.isUndefined() && current.isValid()) {
  Serial.println(ArdJSON::JSON.stringify(current));
}

The getter returns the effective field value: RAM override first, then saved AppConfig, then the definition default. A RAM-only update is lost on restart; the saved value/default becomes effective again. Choose the persistent or RAM path for a given value. A RAM override can mask a later persistent change for the same ID; there is no API to clear just that override. Prefer separate setting and telemetry IDs when both are needed.

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