Hi All, This is an extension of my previous email "Native browser date / time selectors in Angular".
Based on discussion from that thread, from bug #1834662, and me poking around the JS Intl.DateTimeFormat API, I would like to propose a way to streamline and simplify how we handle locale-friendly dates and times in the Angular application. Assumptions: 1. We need to support timezone database names as listed in https://en.wikipedia.org/wiki/List_of_tz_database_time_zones (e.g. Europe/Prague, America/Vancouver, etc.) since this is the documented basis for "lib.timezone" library setting. 2. It is reasonable to assume dates generated by the web browser (via Intl.DateTimeFormat API) for a given locale are understandable by users in said locale and that we don't need to allow users to specify custom date formats. (See examples below) 3. Browsers will be configured to the user's desired locale. 4. Short / numeric dates and times are sufficient to convey the needed information to users. In other words, for en-US, "10/24/2019" is as good as (or better than) "Thursday, October 24 2019" (or similar variations). For example, here's a list numeric date+time strings generated the Intl.DateTimeFormat for a variety of locales: cs-CZ ==> 22. 8. 2019 16:45 en-CA ==> 2019-08-22, 4:45 p.m. fi-FI ==> 22.8.2019 klo 16.45 fr-CA ==> 2019-08-22 16 h 45 hy-AM ==> 2019-8-22 16:45 es-ES ==> 22/8/2019 16:45 ru-RU ==> 22.08.2019, 16:45 en-US ==> 8/22/2019, 4:45 PM 5. We need exactly 3 date/time flavors: date only, time only, and date + time. 6. For time displays, we need hours and minutes, but not seconds. Assuming the above, here's my proposal. 1. Migrate to native browser date and time inputs. With these, we get exactly 1 type of value from each widget (YYYY-MM-DD, hh:mm:ss) so we never have to parse locale-variant date strings. (No MomentJS dependency) 2. Avoid using Angular DatePipe. It does not support the long-form timezone names we use (https://github.com/angular/angular/issues/20225). 3. Teach our FormatService to use Intl.DateTimeFormat when generating date strings. It will support options to produce date, time, or date + time, using the 'short' formats noted above, plus optional timezone and locale parameters. 4. Remove the date / time format library settings once fully migrated to Angular. All that's needed is locale and time zone. As is often the case, I write code before I write emails, so I've mostly implemented everything I've discussed here -- minus an <eg-time-select/> widget -- in the code for https://bugs.launchpad.net/evergreen/+bug/1840782 It also includes a sandbox date/time generator tool where you can pick locales and time zones and see what it produces. I can say with confidence what I'm describing works in Chrome and Firefox, so the question boils down to whether the assumptions I've laid out are reasonable. Thoughts appreciated, Thanks -b
