[chore] Upgrade date-fns to v4

[ggdouglas]

Builds on #7632 (upgrade to date-fns v3), related to #6744

Summary

Upgrades date-fns from v3.6.0 to v4.1.0 and migrates from the third-party date-fns-tz package to the official @date-fns/tz package with first-class timezone support.

Changes

Package Updates

• @blueprintjs/datetime: date-fns ^3.6.0 → ^4.1.0, removed date-fns-tz, added @date-fns/tz ^1.2.0
• @blueprintjs/datetime2: date-fns ^3.6.0 → ^4.1.0
• @blueprintjs/docs-app: date-fns ^3.6.0 → ^4.1.0

Migration to @date-fns/tz

Replaced the third-party date-fns-tz package with the official @date-fns/tz package, which provides first-class timezone support in date-fns v4.

1. Timezone Formatting

- import { formatInTimeZone } from "date-fns-tz";
+ import { tz } from "@date-fns/tz";
+ import { format } from "date-fns";

- formatInTimeZone(date, timezone, formatStr)
+ format(date, formatStr, { in: tz(timezone) })

2. Timezone Offset Calculation

The API changed from returning milliseconds to returning minutes:

- import { getTimezoneOffset } from "date-fns-tz";
+ import { tzOffset } from "@date-fns/tz";

- const offsetInMs = getTimezoneOffset(timezone, date);
- const offsetInMinutes = offsetInMs / 1000 / 60;
+ const offsetInMinutes = tzOffset(timezone, date);
+ const offsetInMs = offsetInMinutes * 60 * 1000;

3. Timezone Conversion Functions

Reimplemented convertLocalDateToTimezoneTime and convertDateToLocalEquivalentOfTimezoneTime using tzOffset instead of toZonedTime/fromZonedTime:

// Equivalent to the old toZonedTime
export function convertLocalDateToTimezoneTime(date: Date, newTimezone: string) {
    const currentOffset = tzOffset(getCurrentTimezone(), date);
    const newOffset = tzOffset(newTimezone, date);
    const offsetDiff = newOffset - currentOffset;
    return new Date(date.getTime() + offsetDiff * 60 * 1000);
}

// Equivalent to the old fromZonedTime
export function convertDateToLocalEquivalentOfTimezoneTime(date: Date, newTimezone: string) {
    const currentOffset = tzOffset(getCurrentTimezone(), date);
    const newOffset = tzOffset(newTimezone, date);
    const offsetDiff = newOffset - currentOffset;
    return new Date(date.getTime() - offsetDiff * 60 * 1000);
}

Breaking Changes

None for consumers of @blueprintjs/datetime. All changes are internal implementation details. The public API remains unchanged.

Documentation

• date-fns v4 changelog
• date-fns v4.0 blog post
• @date-fns/tz documentation

[changelog-app]

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• Migration (Automatically moving data/functionality to a new system)

Description

[chore] Upgrade date-fns to v4

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[chore] Upgrade date-fns to v4

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[chore] Upgrade date-fns to v4

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[svc-palantir-github]

Update `date-fns` to v4

Build artifact links for this commit: documentation | landing | table | demo

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