Add a workaround for a possible null offset ID.

app/src/main/java/org/schabi/newpipe/ktx/OffsetDateTime.kt

@@ -1,10 +1,29 @@
 package org.schabi.newpipe.ktx
 
 import java.time.OffsetDateTime
-import java.time.ZoneId
+import java.time.ZoneOffset
+import java.time.temporal.ChronoField
 import java.util.Calendar
+import java.util.Date
 import java.util.GregorianCalendar
+import java.util.TimeZone
 
-fun OffsetDateTime.toCalendar(zoneId: ZoneId = ZoneId.systemDefault()): Calendar {
-    return GregorianCalendar.from(if (zoneId != offset) atZoneSameInstant(zoneId) else toZonedDateTime())
+// This method is a modified version of GregorianCalendar.from(ZonedDateTime).
+// Math.addExact() and Math.multiplyExact() are desugared even though lint displays a warning.
+@SuppressWarnings("NewApi")
+fun OffsetDateTime.toCalendar(): Calendar {
+    val cal = GregorianCalendar(TimeZone.getTimeZone("UTC"))
+    val offsetDateTimeUTC = withOffsetSameInstant(ZoneOffset.UTC)
+    cal.gregorianChange = Date(Long.MIN_VALUE)
+    cal.firstDayOfWeek = Calendar.MONDAY
+    cal.minimalDaysInFirstWeek = 4
+    try {
+        cal.timeInMillis = Math.addExact(
+            Math.multiplyExact(offsetDateTimeUTC.toEpochSecond(), 1000),
+            offsetDateTimeUTC[ChronoField.MILLI_OF_SECOND].toLong()
+        )
+    } catch (ex: ArithmeticException) {
+        throw IllegalArgumentException(ex)
+    }
+    return cal
 }

app/src/main/java/org/schabi/newpipe/util/Localization.java

@@ -20,6 +20,7 @@ import org.ocpsoft.prettytime.units.Decade;
 import org.schabi.newpipe.R;
 import org.schabi.newpipe.extractor.ListExtractor;
 import org.schabi.newpipe.extractor.localization.ContentCountry;
+import org.schabi.newpipe.ktx.OffsetDateTimeKt;
 
 import java.math.BigDecimal;
 import java.math.RoundingMode;
@@ -30,7 +31,6 @@ import java.time.format.DateTimeFormatter;
 import java.time.format.FormatStyle;
 import java.util.Arrays;
 import java.util.Calendar;
-import java.util.GregorianCalendar;
 import java.util.List;
 import java.util.Locale;
 
@@ -314,7 +314,7 @@ public final class Localization {
     }
 
     public static String relativeTime(final OffsetDateTime offsetDateTime) {
-        return relativeTime(GregorianCalendar.from(offsetDateTime.toZonedDateTime()));
+        return relativeTime(OffsetDateTimeKt.toCalendar(offsetDateTime));
     }
 
     public static String relativeTime(final Calendar calendarTime) {

app/src/test/java/org/schabi/newpipe/ktx/OffsetDateTimeToCalendarTest.kt

@@ -0,0 +1,31 @@
+package org.schabi.newpipe.ktx
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import java.time.LocalDate
+import java.time.OffsetDateTime
+import java.time.ZoneId
+import java.time.ZoneOffset
+import java.util.Calendar
+import java.util.TimeZone
+
+class OffsetDateTimeToCalendarTest {
+    @Test
+    fun testRelativeTimeWithCurrentOffsetDateTime() {
+        val calendar = LocalDate.of(2020, 1, 1).atStartOfDay().atOffset(ZoneOffset.UTC)
+                .toCalendar()
+
+        assertEquals(2020, calendar[Calendar.YEAR])
+        assertEquals(0, calendar[Calendar.MONTH])
+        assertEquals(1, calendar[Calendar.DAY_OF_MONTH])
+        assertEquals(0, calendar[Calendar.HOUR])
+        assertEquals(0, calendar[Calendar.MINUTE])
+        assertEquals(0, calendar[Calendar.SECOND])
+        assertEquals(TimeZone.getTimeZone("UTC"), calendar.timeZone)
+    }
+
+    @Test(expected = IllegalArgumentException::class)
+    fun testRelativeTimeWithFarOffOffsetDateTime() {
+        OffsetDateTime.MAX.minusYears(1).toCalendar()
+    }
+}