Drag the "Relative Time" element onto your Bubble page. Keep it visible (it won’t actually render anything on screen). In the element’s property panel:
Set the Date field to the value you want to compare (e.g. Current cell's Comment's Created Date);
(Optional) Set a refresh interval (in milliseconds);
(Optional) Tick Hide Suffix to remove terms like "ago" or "in";
(Optional) Set a Baseline Date to compare your selected date to another dynamic date instead of the current time;
Select the desired language using the Language Code dropdown.
Add a Text element on the page and set its value to the current value of the Relative Time element.
Example: "Posted " + Relative Time's current value → "Posted 3 hours ago"

Language (required):

You can either:
Select a language from the dropdown ("Language Code Dropdown"), OR
Pass a dynamic language code (e.g. from another dropdown) via the "Language Code Dynamic" field
If both are filled, the dynamic value will override the dropdown


Notes:
You can reference the Relative Time’s current value inside workflows.
You can have multiple instances on the same page, or use it inside repeating groups.
No need to include any external scripts — locales are loaded dynamically based on the selected language.