The `AnnotationLayer` may not display correctly formatted data in PopupAnnotations, especially in the GENERIC viewer, since it's using native methods[1] that depend on the *browser* locale instead of the viewer locale as intended.
With Fluent we're able to improve things since it's got built-in support for formatting dates. Not only does this simplify the JavaScript code slightly, but it also gives the localizer more fine-grained control of the desired output.
Please find additional information here:
- https://projectfluent.org/fluent/guide/builtins.html
- https://projectfluent.org/fluent/guide/functions.html
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[1] `toLocaleDateString`, and `toLocaleTimeString`.