if (format == null) {
        format =
          SimpleDateFormat(BROWSER_COMPATIBLE_DATE_FORMAT_STRINGS[i], Locale.US).apply {
            // Set the timezone to use when interpreting formats that don't have a timezone. GMT is
            // specified by RFC 7231.
            timeZone = UTC
          }
        BROWSER_COMPATIBLE_DATE_FORMATS[i] = format
      }
      position.index = 0
      result = format.parse(this, position)

  }

  private fun formatDate(date: Date): String? {
    val rfc1123: DateFormat = SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US)
    rfc1123.timeZone = TimeZone.getTimeZone("GMT")
    return rfc1123.format(date)
  }

import assertk.assertions.isNull
import java.util.Date
import java.util.TimeZone
import org.junit.jupiter.api.AfterEach
import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.Test

class HttpDateTest {
  private lateinit var originalDefault: TimeZone

  @BeforeEach
  fun setUp() {
    originalDefault = TimeZone.getDefault()
    // The default timezone should affect none of these tests: HTTP specified GMT, so we set it to