HowToReleaseLLVM: Add annual release schedule template

[hans]

Thanks, I think having this is super useful!

llvm/docs/HowToReleaseLLVM.rst

53

Why not a rough date like for the even ones, instead of 4th Tue?

[probinson]

I think "Week number" is too ambiguous to be a guide. If January starts on the last day of the week, does that still count as week#1? What day does the week start on, anyway--much of the world starts the week on Sunday, much of the world starts the week on Monday.
"Fourth Tuesday in January/July" is unambiguous and makes everything easier to plan. Using "Start + N weeks" for the rest of the target dates is fine.

[tstellar]

In D95114#2512315, @probinson wrote:

I think "Week number" is too ambiguous to be a guide. If January starts on the last day of the week, does that still count as week#1? What day does the week start on, anyway--much of the world starts the week on Sunday, much of the world starts the week on Monday.
"Fourth Tuesday in January/July" is unambiguous and makes everything easier to plan. Using "Start + N weeks" for the rest of the target dates is fine.

The whole table is meant to be a guide and not exact. I like having the approximate calendar dates, because I think this is the most informative for non-release managers. The week numbers are really meant for the release manager, but I would be fine replacing those with deltas (e.g. + 4 weeks) if you think that made more sense.

[probinson]

I'd expect the pace of preparing the release to be basically the same regardless of start date, so the milestones would make more sense as start date plus N weeks.
If you want wiggle room for the start date, that's fine, anything that expresses "late January" and "late July" will work. I thought it was going to be more definitive, what with specific week numbers and all.