Convert date in Kotlin

convertTest.kt

@Test
fun `convert Timezone`() {
    val serverTimeInUTC = "2021-11-19 09:50:36" // Friday 19 Nov 2021 at 9:50

    val utcFormatter = SimpleDateFormat(DateUtils.TIMESTAMP_FORMAT)
    utcFormatter.timeZone = TimeZone.getTimeZone("UTC")
    val utcDate = utcFormatter.parse(serverTimeInUTC)
    val utcDateString = utcFormatter.format(utcDate)

    val otherFormatter = SimpleDateFormat(DateUtils.TIMESTAMP_FORMAT)
    otherFormatter.timeZone = TimeZone.getTimeZone("Europe/Bucharest")
    val otherDateString = otherFormatter.format(utcDate)

    println("serverTime: $utcDateString, converted time: $otherDateString")

    assertNotEquals(utcDateString, otherDateString)
}

@Test
fun `convert timestamp`() {
    val serverTimestamp = 1637678180000L // 23 November 2021 14:36 UTC

    val utcTimeZone = TimeZone.getTimeZone("UTC")
    val serverCalendar = Calendar.getInstance(utcTimeZone)
    serverCalendar.timeInMillis = serverTimestamp

    val localTimezone = TimeZone.getTimeZone("Europe/Rome")
    val localCalendar = Calendar.getInstance(localTimezone)
    localCalendar.timeInMillis = serverTimestamp

    // this is just to compare the times in an easy way
    val formatter = SimpleDateFormat(DateUtils.TIMESTAMP_FORMAT)
    formatter.timeZone = utcTimeZone
    val serverTimeInUTC = formatter.format(serverCalendar.time)
    formatter.timeZone = localTimezone
    val localTime = formatter.format(localCalendar.time)

    println("serverTime: $serverTimeInUTC, converted time: $localTime")

    assertNotEquals(serverTimeInUTC, localTime)
}