private const val TIME_STAMP_FORMAT = "EEEE. MMM d, yyyy - hh:mm:ss a"
private const val DATE_FORMAT = "yyyy-MM-dd"

fun Long.getTimeStamp(): String {
    val date = Date(this)
    val simpleDateFormat = SimpleDateFormat(TIME_STAMP_FORMAT, Locale.getDefault())
    simpleDateFormat.timeZone = TimeZone.getDefault()
    return simpleDateFormat.format(date)
}

fun Long.getYearMonthDay(): String {
    val date = Date(this)
    val simpleDateFormat = SimpleDateFormat(DATE_FORMAT, Locale.getDefault())
    simpleDateFormat.timeZone = TimeZone.getDefault()
    return simpleDateFormat.format(date)
}

@Throws(ParseException::class)
fun String.getDateUnixTime(): Long {
    try {
        val simpleDateFormat = SimpleDateFormat(DATE_FORMAT, Locale.getDefault())
        simpleDateFormat.timeZone = TimeZone.getDefault()
        return simpleDateFormat.parse(this)!!.time
    } catch (e: ParseException) {
        e.printStackTrace(0)
    }
    throw ParseException("Please Enter a valid date", 0)
}

val currentTime = System.currentTimeMillis()
println(currentTime.getTimeStamp()) 
// Sunday, September 20, 2020 - 10:48:26 AM
println(currentTime.getYearMonthDay())
// 2020-09-20
println("2020-09-20".getDateUnixTime())
// 1600549200000