fix date timezone issues: use JST for GW events, local time for user dates

src/lib/components/crew/InvitationsModal.svelte

@@ -13,6 +13,7 @@
 	import ModalBody from '$lib/components/ui/ModalBody.svelte'
 	import Button from '$lib/components/ui/Button.svelte'
 	import Icon from '$lib/components/Icon.svelte'
+	import { formatDate } from '$lib/utils/date'
 	import type { CrewInvitation, PhantomPlayer } from '$lib/types/api/crew'
 
 	interface Props {
@@ -98,15 +99,6 @@
 		}
 	}
 
-	// Format date
-	function formatDate(dateString: string): string {
-		return new Date(dateString).toLocaleDateString(undefined, {
-			year: 'numeric',
-			month: 'short',
-			day: 'numeric'
-		})
-	}
-
 	// Check if invitation is expired
 	function isExpired(expiresAt: string): boolean {
 		return new Date(expiresAt) < new Date()

src/lib/components/crew/MemberRow.svelte

@@ -6,6 +6,7 @@
 	import DropdownMenu from '$lib/components/ui/DropdownMenu.svelte'
 	import { DropdownMenu as DropdownMenuBase } from 'bits-ui'
 	import { crewStore } from '$lib/stores/crew.store.svelte'
+	import { formatDate } from '$lib/utils/date'
 	import type { CrewMembership } from '$lib/types/api/crew'
 
 	interface Props {
@@ -40,14 +41,6 @@
 		}
 	}
 
-	function formatDate(dateString: string): string {
-		return new Date(dateString).toLocaleDateString(undefined, {
-			year: 'numeric',
-			month: 'short',
-			day: 'numeric'
-		})
-	}
-
 	const canShowOfficerActions = $derived(
 		crewStore.isOfficer &&
 			crewStore.canActOnMember(member.role) &&

src/lib/components/crew/PhantomRow.svelte

@@ -5,6 +5,7 @@
 	import DropdownMenu from '$lib/components/ui/DropdownMenu.svelte'
 	import { DropdownMenu as DropdownMenuBase } from 'bits-ui'
 	import { crewStore } from '$lib/stores/crew.store.svelte'
+	import { formatDate } from '$lib/utils/date'
 	import type { PhantomPlayer } from '$lib/types/api/crew'
 
 	interface Props {
@@ -20,14 +21,6 @@
 	const { phantom, currentUserId, onEdit, onDelete, onAssign, onAccept, onDecline }: Props =
 		$props()
 
-	function formatDate(dateString: string): string {
-		return new Date(dateString).toLocaleDateString(undefined, {
-			year: 'numeric',
-			month: 'short',
-			day: 'numeric'
-		})
-	}
-
 	// Status badge type
 	type ClaimStatus = 'unclaimed' | 'pending' | 'claimed'
 

src/lib/utils/date.ts

@@ -0,0 +1,49 @@
+/**
+ * Format a date string in JST (Japan Standard Time).
+ * Use this for game-related dates like GW events, as Granblue Fantasy uses JST.
+ */
+export function formatDateJST(
+	dateString: string,
+	options: Intl.DateTimeFormatOptions = {
+		year: 'numeric',
+		month: 'short',
+		day: 'numeric'
+	}
+): string {
+	return new Date(dateString).toLocaleDateString(undefined, {
+		...options,
+		timeZone: 'Asia/Tokyo'
+	})
+}
+
+/**
+ * Format a date string in local time.
+ * Use this for user-related dates like join dates, invitation expiries, etc.
+ *
+ * For date-only strings (YYYY-MM-DD), appends T00:00:00 to parse as local midnight
+ * instead of UTC midnight, preventing the date from shifting.
+ */
+export function formatDate(
+	dateString: string,
+	options: Intl.DateTimeFormatOptions = {
+		year: 'numeric',
+		month: 'short',
+		day: 'numeric'
+	}
+): string {
+	// If it's a date-only string (YYYY-MM-DD), parse as local time
+	const dateToFormat =
+		dateString.length === 10 ? new Date(dateString + 'T00:00:00') : new Date(dateString)
+	return dateToFormat.toLocaleDateString(undefined, options)
+}
+
+/**
+ * Format a date string with long month format in JST (e.g., "June 21, 2025")
+ */
+export function formatDateLongJST(dateString: string): string {
+	return formatDateJST(dateString, {
+		year: 'numeric',
+		month: 'long',
+		day: 'numeric'
+	})
+}

src/routes/(app)/crew/+page.svelte

@@ -14,6 +14,7 @@
 	import ModalFooter from '$lib/components/ui/ModalFooter.svelte'
 	import Input from '$lib/components/ui/Input.svelte'
 	import CrewHeader from '$lib/components/crew/CrewHeader.svelte'
+	import { formatDateJST } from '$lib/utils/date'
 	import type { PageData } from './$types'
 
 	interface Props {
@@ -159,15 +160,6 @@
 		settingsError = null
 	}
 
-	// Helper for formatting dates
-	function formatDate(dateString: string): string {
-		return new Date(dateString).toLocaleDateString(undefined, {
-			year: 'numeric',
-			month: 'short',
-			day: 'numeric'
-		})
-	}
-
 	// Helper for formatting scores with commas
 	function formatScore(score: number): string {
 		return score.toLocaleString()
@@ -296,7 +288,7 @@
 									</span>
 								</div>
 								<span class="event-dates">
-									{formatDate(event.startDate)} – {formatDate(event.endDate)}
+									{formatDateJST(event.startDate)} – {formatDateJST(event.endDate)}
 								</span>
 								<span class="event-score">
 									{#if event.crewTotalScore !== undefined}

src/routes/(app)/crew/events/[eventNumber]/+page.svelte

@@ -21,6 +21,7 @@
 	import EditCrewScoreModal from '$lib/components/crew/EditCrewScoreModal.svelte'
 	import SegmentedControl from '$lib/components/ui/segmented-control/SegmentedControl.svelte'
 	import Segment from '$lib/components/ui/segmented-control/Segment.svelte'
+	import { formatDateJST } from '$lib/utils/date'
 	import {
 		GW_ROUND_LABELS,
 		type GwRound,
@@ -159,15 +160,6 @@
 		return parseInt(value.replace(/,/g, ''), 10)
 	}
 
-	// Format date
-	function formatDate(dateString: string): string {
-		return new Date(dateString).toLocaleDateString(undefined, {
-			year: 'numeric',
-			month: 'short',
-			day: 'numeric'
-		})
-	}
-
 	// Navigate back
 	function handleBack() {
 		goto('/crew')
@@ -406,7 +398,7 @@
 							{elementLabels[gwEvent.element] ?? 'Unknown'}
 						</span>
 						<span class="event-dates">
-							{formatDate(gwEvent.startDate)} – {formatDate(gwEvent.endDate)}
+							{formatDateJST(gwEvent.startDate)} – {formatDateJST(gwEvent.endDate)}
 						</span>
 					</div>
 					<div class="tab-control">

src/routes/(app)/crew/join/+page.svelte

@@ -8,6 +8,7 @@
 	import { useAcceptInvitation, useRejectInvitation } from '$lib/api/mutations/crew.mutations'
 	import { crewStore } from '$lib/stores/crew.store.svelte'
 	import Button from '$lib/components/ui/Button.svelte'
+	import { formatDate } from '$lib/utils/date'
 	import type { PageData } from './$types'
 
 	interface Props {
@@ -61,15 +62,6 @@
 		}
 	}
 
-	// Format date
-	function formatDate(dateString: string): string {
-		return new Date(dateString).toLocaleDateString(undefined, {
-			year: 'numeric',
-			month: 'short',
-			day: 'numeric'
-		})
-	}
-
 	// Check if invitation is expired
 	function isExpired(expiresAt: string): boolean {
 		return new Date(expiresAt) < new Date()

src/routes/(app)/crew/members/+page.svelte

@@ -29,6 +29,7 @@
 	import AssignPhantomModal from '$lib/components/crew/AssignPhantomModal.svelte'
 	import ConfirmClaimModal from '$lib/components/crew/ConfirmClaimModal.svelte'
 	import { DropdownMenu as DropdownMenuBase } from 'bits-ui'
+	import { formatDate } from '$lib/utils/date'
 	import type {
 		MemberFilter,
 		CrewMembership,
@@ -303,15 +304,6 @@
 		}
 	}
 
-	// Format date
-	function formatDate(dateString: string): string {
-		return new Date(dateString).toLocaleDateString(undefined, {
-			year: 'numeric',
-			month: 'short',
-			day: 'numeric'
-		})
-	}
-
 	// Check if invitation is expired
 	function isInvitationExpired(expiresAt: string): boolean {
 		return new Date(expiresAt) < new Date()

src/routes/(app)/database/gw-events/+page.svelte

@@ -7,6 +7,7 @@
 	import { createQuery } from '@tanstack/svelte-query'
 	import { gwAdapter } from '$lib/api/adapters/gw.adapter'
 	import Button from '$lib/components/ui/Button.svelte'
+	import { formatDateJST } from '$lib/utils/date'
 	import type { GwEvent } from '$lib/types/api/gw'
 	import type { PageData } from './$types'
 
@@ -61,15 +62,6 @@
 		)
 	})
 
-	// Format date for display
-	function formatDate(dateString: string): string {
-		return new Date(dateString).toLocaleDateString(undefined, {
-			year: 'numeric',
-			month: 'short',
-			day: 'numeric'
-		})
-	}
-
 	// Navigate to event detail/edit
 	function handleRowClick(event: GwEvent) {
 		goto(`/database/gw-events/${event.id}`)
@@ -124,7 +116,7 @@
 								</td>
 								<td class="col-dates">
 									<span class="dates">
-										{formatDate(event.startDate)} - {formatDate(event.endDate)}
+										{formatDateJST(event.startDate)} - {formatDateJST(event.endDate)}
 									</span>
 								</td>
 							</tr>

src/routes/(app)/database/gw-events/[id]/+page.svelte

@@ -9,6 +9,7 @@
 	import DetailsContainer from '$lib/components/ui/DetailsContainer.svelte'
 	import DetailItem from '$lib/components/ui/DetailItem.svelte'
 	import SidebarHeader from '$lib/components/ui/SidebarHeader.svelte'
+	import { formatDateJST, formatDateLongJST } from '$lib/utils/date'
 	import type { PageData } from './$types'
 
 	interface Props {
@@ -52,15 +53,6 @@
 		6: 'light'
 	}
 
-	// Format date for display
-	function formatDate(dateString: string): string {
-		return new Date(dateString).toLocaleDateString(undefined, {
-			year: 'numeric',
-			month: 'long',
-			day: 'numeric'
-		})
-	}
-
 	// Navigate to edit
 	function handleEdit() {
 		goto(`/database/gw-events/${eventId}/edit`)
@@ -102,15 +94,15 @@
 						{elementLabels[event.element] ?? 'Unknown'}
 					</span>
 				</DetailItem>
-				<DetailItem label="Start Date" value={formatDate(event.startDate)} />
-				<DetailItem label="End Date" value={formatDate(event.endDate)} />
+				<DetailItem label="Start Date" value={formatDateLongJST(event.startDate)} />
+				<DetailItem label="End Date" value={formatDateLongJST(event.endDate)} />
 			</DetailsContainer>
 
 			{#if event.createdAt}
 				<DetailsContainer title="Metadata">
-					<DetailItem label="Created" value={formatDate(event.createdAt)} />
+					<DetailItem label="Created" value={formatDateJST(event.createdAt)} />
 					{#if event.updatedAt}
-						<DetailItem label="Updated" value={formatDate(event.updatedAt)} />
+						<DetailItem label="Updated" value={formatDateJST(event.updatedAt)} />
 					{/if}
 				</DetailsContainer>
 			{/if}