Date and Time methods
These methods are intended to format date and time using the Home Assistant native logic.
When you open Home Assistant and it is loading, it is possible that the locale data is not ready yet until the system finished to load all the resources. If you try to render a template using the methods to format dates and time at the beginning of this loading process, it is possible that the formatting wouldn't follow your language settings. This will be corrected if the template is reevaluated later, but to avoid any wrong formatting at the beginning, it is recommended to delay the formatting in the first rendering using a Promise or to force a re-rendering of the template using JavaScript reactive variables or any other technique that mitigates this issue.
The methods to format dates and time depend on the locale that the user has configured in Home Assistant, so the result of these methods is not deterministic. For the examples, a specific locale has been used.
formatDate
This method formats a date using the Home Assistant locale. It accepts a date, a string [ISO 8601] representation of a date or a number representing the [timestamp] in milliseconds.
// The result of all this examples will be "December 14, 2025"
// Using a date string
formatDate('2025-12-14');
// Using an ISO 8601 date string
formatDate('2025-12-14T00:00:00');
// Using a timestamp number
formatDate(1765715953817);
// Using a date
formatDate(new Date(2025, 11, 14));
formatDateTime
This method formats a date with time using the Home Assistant locale. It accepts a date, a string [ISO 8601] representation of a date or a number representing the [timestamp] in milliseconds.
// The result of all this examples will be "December 14, 2025 at 12:00 AM"
// Using an ISO 8601 date string
formatDateTime('2025-12-14T00:00:00');
// Using a timestamp number
formatDateTime(1765666800000);
// Using a date
formatDateTime(new Date(2025, 11, 14, 0, 0, 0));
formatTime
This method formats a time using the Home Assistant locale. It accepts a date, a string [ISO 8601] representation of a date, a number representing the [timestamp] in milliseconds, or a string representation of a time in the format HH:MM or HH:MM:SS.
// The result of all this examples will be "12:00 AM"
// Using a time string
formatTime('00:00'); // It could also include seconds 00:00:00
// Using an ISO 8601 date string
formatTime('2025-12-14T00:00:00');
// Using a timestamp number
formatTime(1765666800000);
// Using a date
formatTime(new Date(2025, 11, 14, 0, 0, 0));
getRelativeTime
This method get the relative time of a date using the Home Assistant locale. It accepts a date, a string [ISO 8601] representation of a date or a number representing the [timestamp] in milliseconds. This method also accepts a secondary optional boolean parameter to define if the result should be capitalized or not (by default it is false).
// The result of all this examples will be "in 2 weeks"
// Assuming that the current date is December 1st, 2025 at 12:00 AM
// Using an ISO 8601 date string
getRelativeTime('2025-12-14T00:00:00');
// Using a timestamp number
getRelativeTime(1765666800000);
// Using a date
getRelativeTime(new Date(2025, 11, 14, 0, 0, 0));