cache entries to help with header stutter

Shared/Random.swift

@@ -34,11 +34,17 @@ class Random {
         return updateTime
     }
     
+    static var existingWeekdayName = [Int: String]()
     static func weekdayName(fromDate date: Date) -> String {
         let weekday = Calendar.current.component(.weekday, from: date)
         let calendar = Calendar.current
         let dayIndex = ((weekday - 1) + (calendar.firstWeekday - 1)) % 7
-        return calendar.weekdaySymbols[dayIndex]
+        if let value = Random.existingWeekdayName[dayIndex] {
+            return value
+        }
+        let newValue = calendar.weekdaySymbols[dayIndex]
+        Random.existingWeekdayName[dayIndex] = newValue
+        return newValue
     }
     
     static func monthName(fromMonthInt: Int) -> String {
@@ -46,13 +52,20 @@ class Random {
         return monthName
     }
     
+    static var existingDayFormat = [NSNumber: String]()
     static func dayFormat(fromDate date: Date) -> String {
         let components = Calendar.current.dateComponents([.day], from: date)
         let day = components.day!
         
         let formatter = NumberFormatter()
         formatter.numberStyle = .ordinal
-        return formatter.string(from: NSNumber(integerLiteral: day)) ?? ""
+        let num = NSNumber(integerLiteral: day)
+        if let value = existingDayFormat[num] {
+            return value
+        }
+        let newValue = formatter.string(from: num) ?? ""
+        existingDayFormat[num] = newValue
+        return newValue
     }
     
     static func createTotalPerc(fromEntries entries: [MoodEntry]) -> [MoodMetrics] {