convertDateToReadableStringFunction.swift

func convertDateToReadableString(dateToConvert: Date) -> String {
    /// Make a date formatter object. This will take care converting Date objects to String objects and vice versa.
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "MMddyy" /// This is a pretty good format that will yield something like "January 1, 2020"
    let todaysDate = Date() /// When you initialize a Date object like this, the Date will be the current date.
    let todaysDateAsString = dateFormatter.string(from: todaysDate)
    let yesterday = todaysDate.subtract(days: 1)
    let yesterdaysDateAsString = dateFormatter.string(from: yesterday!)

    let oneWeekAgo = todaysDate.subtract(days: 7)
    let dayBeforeYesterday = yesterday?.subtract(days: 1)
    let range = oneWeekAgo!...dayBeforeYesterday!

    let stringDate = dateFormatter.string(from: dateToConvert)
    /// This will be the date that you want to convert as a String
    
    /// Now, we do some simple if/else checks.
    if stringDate == todaysDateAsString {
        return "Today"
    } else if stringDate == yesterdaysDateAsString {
        return "Yesterday"
    } else {
        if range.contains(dateToConvert) {
            dateFormatter.dateFormat = "EEEE"
            return dateFormatter.string(from: dateToConvert)
        } else {
            dateFormatter.dateFormat = "MMMM d',' yyyy"
            return dateFormatter.string(from: dateToConvert)
        }
    }
}
    
extension Date {
    func add(years: Int = 0, months: Int = 0, days: Int = 0, hours: Int = 0, minutes: Int = 0, seconds: Int = 0) -> Date? {
        let comp = DateComponents(year: years, month: months, day: days, hour: hours, minute: minutes, second: seconds)
        return Calendar.current.date(byAdding: comp, to: self)
    }
    
    func subtract(years: Int = 0, months: Int = 0, days: Int = 0, hours: Int = 0, minutes: Int = 0, seconds: Int = 0) -> Date? {
        return add(years: -years, months: -months, days: -days, hours: -hours, minutes: -minutes, seconds: -seconds)
    }
}