fix(core, achievements): Account age due to leap years

[spenserblack]

Sorry to spam PRs (#499). Looks like I can't re-open a PR after a force-push.

This creates a new date created from the diff. The UTC year of that new date is used. Because it's created from a diff, that date is equal to the diff + 1970, so 1970 is subtracted from the year to get the year diff.

I wasn't able to write any automated tests (looks like a lot of refactoring would have to happen for the plugins if we're going to test them), but I've informally tested over leap years, and generated a metrics .svg.

As a simple check, you can do this

#!/usr/bin/env node
const now = new Date('2021-08-24T00:00:00Z');
const created = new Date('2017-08-25T00:00:00Z');

console.log('now:', now);
console.log('created:', created);

console.log('years (old way):', (now - created) / (365 * 24 * 60 * 60 * 1000));
console.log('years (new way):', new Date(now - created).getUTCFullYear() - 1970);

[spenserblack]

Note

Following discussion in #499, it would probably be preferable if the "Member" achievement could increment daily, which this breaks.

[lowlighter]

const { years, months } = computed.registered
const value = years + months/12

May be good enough to mitigate huge progress steps.
If I'm not too bad at maths it would result in 8/4/4/2/2% steps, so it's kind of acceptable if daily increase are tedious to achieve

[spenserblack]

I ended up just adding days / 365.25. It's not a perfectly precise way of calculating the incremental change daily, but I think the change is so small that it's not necessary to add/remove a day if it's a leap year.

[lowlighter]

Happy "GitHub day" (without leap years) by the way 🥳

[spenserblack]

Happy "GitHub day" (without leap years) by the way

Thank you!
Just made some changes. With these changes to the calculations, hopefully there's a good balance of accuracy and visual quality. Although I'm feeling kind of braindead today TBH, so I may have to review my own code later 😆

[spenserblack]

I tried to keep the git history clean (hence the force-pushes in #499), but the git history has gotten a bit messy again. Please let me know if you want me to rebase at all.

[Nixinova]

I tried to keep the git history clean (hence the force-pushes in #499), but the git history has gotten a bit messy again. Please let me know if you want me to rebase at all.

PRs are squash merged so it should be fine either way

[lowlighter]

Thanks for your contribution 👍 !