Our dependency moment-timezone includes all possible timezones with all date ranges, producing a too big document.js bundle ≃1.24 MiB.
Ideally we should be able to load asynchronously each timezone.
However, for a quick and short term solution I suggest to remove all dates that are after the next year (current year of the bundle generation + 1 to avoid glitches at the beginning of 2020). In document view, the only purpose of moment-timezone is to display last update date of a document (date which is in the past). There is no plan to manage dates in the future.
By using https://github.com/gilmoreorless/moment-timezone-data-webpack-plugin, we can significantly reduce the size of the bundle.