[RFC 0080] Change NixOS releases to YY.05,YY.11 (#80)

rfcs/0080-nixos-release-schedule.md

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+---
+feature: nixos-release-schedule
+start-date: 2020-11-28
+author: Jonathan Ringer (@jonringer)
+co-authors: Frederik Rietdijk (@FRidh)
+shepherd-team: @ryantm, @domenkozar and @garbas
+related-issues:
+---
+
+# Summary
+[summary]: #summary
+
+NixOS is released twice a year; the current release schedule targets March
+and September for the release months. However, trying to provide a polished
+desktop-user experience is difficult and moving the target release months to
+May and November should minimize the amount of in-house work needed to
+cut a release.
+
+# Motivation
+[motivation]: #motivation
+
+By changing our release dates to follow those of certain upstream projects,
+we could reduce the amount of issues we encounter during stabilization.
+In particular, GNOME and KDE Plasma both have a release in September, which
+allows ample time for NixOS contributors to package and stabilize the
+desktop managers before the November release. For the May release, GNOME will
+have a similar stabilization period; while Plasma, which has a four month
+release cadence, will have a slightly older but still supported non-LTS
+release. Using LTS releases is not feasible as there is no guarantee that
+they will be compatible with the version of systemd during branch-off.
+
+The current March and September release months may be the worst months for
+GNOME and Plasma, as the release available during stabilization would be
+End-of-Life a few weeks after the target release date. Also, this period marks
+the greatest potential dependency "drift" from development on unstable. For example,
+many of the 20.09 release blockers were related to issues with systemd-246 and plasma-5.18,
+however, plasma-5.19 and the yet-released 5.20 both supported systemd-246 with
+zero additional effort.
+
+Choosing branch-off points in master where the major desktop manager use
+cases should be well stabilized will allow for release stabilization to
+focus on failing builds and minor issues.
+
+## Core changes
+
+The 21.03 release will be delayed until 21.05, and the current 20.09 release
+will be supported until June 2021. After the initial 21.05 release, all subsequent
+releases will occur six months apart following a YY.05 and YY.11 convention.
+
+# Drawbacks
+[drawbacks]: #drawbacks
+
+There will be some initial confusion with stable users as to why the 21.03
+release was delayed.
+
+# Alternatives
+[alternatives]: #alternatives
+
+## Maintain the status quo regarding release dates
+
+We could keep the release dates in March and September. However, we
+would need some other way to minimize the work and risk from trying to
+provide a polished experience for 60,000+ packages, 17 desktop managers,
+and 30+ window managers.
+
+# Future work
+[future]: #future-work
+
+- Update .version on master to 21.05
+- Update unstable osinfo-db entry to 21.05pre
+- Document the release schedule in the NixOS manual.
+- Announce the various deadlines on the mailing list (Discourse).