Add ChartDateFormatter and wire into header

ios/Packages/PrimitivesComponents/Package.swift

@@ -60,6 +60,7 @@ let package = Package(
                 "PrimitivesComponents",
                 "PrimitivesComponentsTestKit",
                 "GemstonePrimitives",
+                "Formatters",
             ],
         ),
     ],

ios/Packages/PrimitivesComponents/Sources/Formatters/ChartDateFormatter.swift

@@ -0,0 +1,34 @@
+// Copyright (c). Gem Wallet. All rights reserved.
+
+import Foundation
+import Formatters
+import Primitives
+
+public struct ChartDateFormatter: Sendable {
+    private let relative: RelativeDateFormatter
+    private let locale: Locale
+    private let timeZone: TimeZone
+
+    public init(
+        relative: RelativeDateFormatter = RelativeDateFormatter(),
+        locale: Locale = .current,
+        timeZone: TimeZone = .current,
+    ) {
+        self.relative = relative
+        self.locale = locale
+        self.timeZone = timeZone
+    }
+
+    public func string(for date: Date, period: ChartPeriod) -> String {
+        switch period {
+        case .hour: date.formatted(dateTime.hour().minute())
+        case .day: relative.string(from: date)
+        case .week, .month: date.formatted(dateTime.month(.abbreviated).day().hour().minute())
+        case .year, .all: date.formatted(dateTime.year().month(.abbreviated).day())
+        }
+    }
+
+    private var dateTime: Date.FormatStyle {
+        Date.FormatStyle(locale: locale, timeZone: timeZone)
+    }
+}

ios/Packages/PrimitivesComponents/Sources/Types/ChartHeaderViewModel.swift

@@ -16,6 +16,7 @@ public struct ChartHeaderViewModel {
     public let type: ChartValueType
 
     private let formatter: CurrencyFormatter
+    private let dateFormatter: ChartDateFormatter
 
     public init(
         period: ChartPeriod,
@@ -24,6 +25,7 @@ public struct ChartHeaderViewModel {
         priceChangePercentage: Double,
         headerValue: Double? = nil,
         formatter: CurrencyFormatter,
+        dateFormatter: ChartDateFormatter = ChartDateFormatter(),
         type: ChartValueType = .price,
     ) {
         self.period = period
@@ -33,24 +35,15 @@ public struct ChartHeaderViewModel {
         self.headerValue = headerValue
         self.type = type
         self.formatter = formatter
+        self.dateFormatter = dateFormatter
     }
 
     private var valueChange: PriceChangeViewModel? {
         type == .priceChange ? PriceChangeViewModel(value: price, currencyFormatter: formatter) : nil
     }
 
     public var dateText: String? {
-        guard let date else { return nil }
-        switch period {
-        case .hour:
-            return date.formatted(.dateTime.hour().minute())
-        case .day:
-            return date.formatted(.dateTime.weekday(.abbreviated).hour().minute())
-        case .week, .month:
-            return date.formatted(.dateTime.month(.abbreviated).day().hour().minute())
-        case .year, .all:
-            return date.formatted(.dateTime.year().month(.abbreviated).day())
-        }
+        date.map { dateFormatter.string(for: $0, period: period) }
     }
 
     public var headerValueText: String? {

ios/Packages/PrimitivesComponents/Tests/PrimitivesComponentsTests/ChartDateFormatterTests.swift

@@ -0,0 +1,37 @@
+// Copyright (c). Gem Wallet. All rights reserved.
+
+import Formatters
+import Foundation
+import Primitives
+@testable import PrimitivesComponents
+import Testing
+
+struct ChartDateFormatterTests {
+    @Test
+    func stringForPeriod() throws {
+        let timeZone = TimeZone.NewYork!
+        let today = try #require(Calendar.current.date(bySettingHour: 14, minute: 30, second: 0, of: Date()))
+        let fixed = Date(timeIntervalSince1970: 1_745_505_000)
+
+        let us = ChartDateFormatter(
+            relative: RelativeDateFormatter(locale: .US, timeZone: timeZone),
+            locale: .US,
+            timeZone: timeZone,
+        )
+        #expect(us.string(for: today, period: .day) == "Today, 2:30 PM")
+        #expect(us.string(for: fixed, period: .hour) == "9:30 AM")
+        #expect(us.string(for: fixed, period: .week) == "Apr 24, 9:30 AM")
+        #expect(us.string(for: fixed, period: .month) == "Apr 24, 9:30 AM")
+        #expect(us.string(for: fixed, period: .year) == "Apr 24, 2025")
+        #expect(us.string(for: fixed, period: .all) == "Apr 24, 2025")
+
+        let de = ChartDateFormatter(
+            relative: RelativeDateFormatter(locale: Locale(identifier: "de_DE"), timeZone: timeZone),
+            locale: Locale(identifier: "de_DE"),
+            timeZone: timeZone,
+        )
+        #expect(de.string(for: today, period: .day) == "Heute, 14:30")
+        #expect(de.string(for: fixed, period: .hour) == "09:30")
+        #expect(de.string(for: fixed, period: .year) == "24. Apr. 2025")
+    }
+}