How to get Thisweek start and end date and Lastweek start and end date in Kotlin

I need to get this week startdate like 2023-02-20 and last week startdate and end date.

startdate will be monday.

so I create 4 variables like below.

private var thisWeekStart : Long = 0
    private var thisWeekEnd : Long = 0
    private var lastWeekStart : Long = 0
    private var lastWeekEnd : Long = 0

And I tried to assign something like below..

var cal = Calendar.getInstance()
        cal.time = Date()
        thisWeekEnd = cal.timeInMillis

        // 이번주 시작
        cal.get(Calendar.DAY_OF_WEEK)
        thisWeekStart = cal.timeInMillis

        cal.add(Calendar.DAY_OF_WEEK, -1)
        lastWeekStart = cal.timeInMillis

        cal.clear()
        cal.set(Calendar.DAY_OF_WEEK, -1)
        lastWeekStart = cal.timeInMillis

But it throws milliseconds not like yyyy-MM-dd format.

And I'm not sure is that correct way of keep clearing calendar like above.

Most of all, I can't get last week's end date with above way.

Is there any good way to get this weed and last week start, end date?

At first, we define our desired output format. In this case we will use yyyy-MM-dd. In the next step we save the current date in a variable. In the third line we define timezone in which we are working (I used Europe/Berlin for testing purposes, bacause I'm in germany).

In the next steps we create Calendar instance for each desired date and manipulate the date to our needs.

Important: You have to add the line firstDayOfWeek = Calendar.MONDAY only if your week starts at another date than Sunday.

val dateFormat = SimpleDateFormat("yyyy-MM-dd")
val today = Calendar.getInstance()
val timeZone = TimeZone.getTimeZone("Europe/Berlin")

val startOfWeek = Calendar.getInstance(timeZone).apply {
    firstDayOfWeek = Calendar.MONDAY
    set(Calendar.DAY_OF_WEEK, Calendar.MONDAY)
}.time

val endOfWeek = Calendar.getInstance(timeZone).apply {
    firstDayOfWeek = Calendar.MONDAY
    set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY)
}.time

val startOfLastWeek = Calendar.getInstance(timeZone).apply {
    firstDayOfWeek = Calendar.MONDAY
    set(Calendar.WEEK_OF_YEAR, today.get(Calendar.WEEK_OF_YEAR) - 1)
    set(Calendar.DAY_OF_WEEK, Calendar.MONDAY)
}.time

val endOfLastWeek = Calendar.getInstance(timeZone).apply {
    firstDayOfWeek = Calendar.MONDAY
    set(Calendar.WEEK_OF_YEAR, today.get(Calendar.WEEK_OF_YEAR) - 1)
    set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY)
}.time

val startOfWeekAsString = dateFormat.format(startOfWeek)
val endOfWeekAsString = dateFormat.format(endOfWeek)
val startOfLastWeekAsString = dateFormat.format(startOfLastWeek)
val endOfLastWeekAsString = dateFormat.format(endOfLastWeek)

println("Start of week: $startOfWeekAsString")
println("End of week: $endOfWeekAsString")
println("Start of last week: $startOfLastWeekAsString")
println("End of last week: $endOfLastWeekAsString")

Expected output:

Start of week: 2023-02-13
End of week: 2023-02-19
Start of last week: 2023-02-06
End of last week: 2023-02-12