fix: correct date display by preventing timezone conversion

[matiasmoya]

Description

Fixes the date offset bug where activity graph tooltips (td title attribute) displayed dates one day before the actual activity data.

Closes #1

Problem

• currentDate is created using Date.UTC(), which creates a UTC date.
• The toLocaleDateString() method on line 143 was converting UTC dates to the user's local timezone, causing a date shift.

For example, if you're in a timezone behind UTC (like America/New_York, UTC-5), a UTC date of 2025-09-29 00:00:00 UTC becomes 2025-09-28 19:00:00 EST in local time, which then displays as 2025-09-28.

Solution

Added { timeZone: 'UTC' } option to toLocaleDateString() to ensure dates are formatted in UTC and match the activity data keys.

Changed

• src/activity-graph-element.js line 143

Before

const text = `${currentDate.toLocaleDateString(lang)} – Activities: ${
    activityData[dateKey] || 0
}`;

After

const text = `${currentDate.toLocaleDateString(lang, { timeZone: 'UTC' })} – Activities: ${
    activityData[dateKey] || 0
}`;

Testing

Tested in GMT-3 timezone:

• ✅ Dates now correctly match the activity data
• ✅ No date shift occurs
• ✅ Tooltip displays the correct date

[mariohamann]

Sorry, just saw your PR. Thanks for digging into it! Didn't have the time to try it myself, but raised a question.

[mariohamann]

Suggested change

	const text = `${currentDate.toLocaleString(lang, {
	timeZone: 'UTC',
	year: 'numeric',
	month: '2-digit',
	day: '2-digit'
	})} – Activities: ${activityData[dateKey] || 0}`;
	const text = `${currentDate.toLocaleString(lang, {
	timeZone: 'UTC'
	})} – Activities: ${activityData[dateKey] || 0}`;

[mariohamann]

Would this work as well?