Warning: GGGG/WW week tokens produce wrong results when used with Periodic Notes plugin in US locale — use gggg/ww instead

[imtheperl]

Context

If you use Templater together with the Periodic Notes plugin for weekly notes, there is a locale-dependent token mismatch that causes your filename and note content to disagree on the week number. This is easy to hit if you try to use ISO week tokens (GGGG, WW) in your weekly note format.

The problem

Periodic Notes generates the filename by calling moment().startOf("week") before formatting. In a US locale (Sunday-start), this snaps Monday back to the previous Sunday. If your template then uses ISO week tokens (GGGG, WW) to display the week number, Templater will show a different (correct) week number because Templater processes the template at file-creation time without the startOf("week") step.

Example on Monday April 27, 2026 (US locale):

What generates it	Token	Result
Periodic Notes (filename)	YYYY-[W]WW applied to Sunday April 26	2026-W17 ❌
Templater (content)	tp.date.now("WW") on Monday April 27	18 ✅

The filename says W17, the content says W18. Extremely confusing to diagnose.

The fix

Use locale week tokens throughout: gggg instead of GGGG, and ww instead of WW. In a Sunday-start locale, gggg-[W]ww applied to Sunday April 26 gives 2026-W18 — agreeing with Templater's output for Monday April 27.

In your Templater weekly template, use:

<%*
const isoDay = parseInt(tp.date.now("E")); // 1=Mon, 7=Sun
const daysToMonday = 1 - isoDay;

// Anchor weekNum and year to Monday so the note is correct
// regardless of what day of the week you open it
const weekNum  = tp.date.now("ww", daysToMonday);
const year     = tp.date.now("gggg", daysToMonday);
const prevWeek = tp.date.now("gggg-[W]ww", -7);
const nextWeek = tp.date.now("gggg-[W]ww", 7);
-%>

Anchoring weekNum and year to Monday (via daysToMonday) is also important — without it, if you open the note on Sunday before midnight, ww will return the previous locale week's number.

And in periodic-notes/data.json (or the Periodic Notes plugin settings UI), set:

Weekly note format: gggg-[W]ww

Who this affects

Anyone in a US/Sunday-start locale using ISO week tokens in their weekly note template combined with the Periodic Notes plugin. This is likely a large portion of US-based users of both plugins.

Root cause (for the curious)

The Periodic Notes plugin calls date.clone().startOf("week") before formatting the filename. startOf("week") and gggg/ww tokens both use the same locale definition of week boundaries. ISO tokens (GGGG/WW) use a fixed Monday-start definition regardless of locale — which diverges from startOf("week") whenever the locale week doesn't start on Monday.