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

Question

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?

Answer 1

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