Use PrettyTime's new formatUnrounded(OffsetDateTime) method.

Also change the types of the relevant variables from Calendar to OffsetDateTime.

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

@@ -1,29 +0,0 @@
-package org.schabi.newpipe.ktx
-
-import java.time.OffsetDateTime
-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
-
-// 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/local/feed/FeedFragment.kt

@@ -45,7 +45,7 @@ import org.schabi.newpipe.ktx.animate
 import org.schabi.newpipe.ktx.animateHideRecyclerViewAllowingScrolling
 import org.schabi.newpipe.local.feed.service.FeedLoadService
 import org.schabi.newpipe.util.Localization
-import java.util.Calendar
+import java.time.OffsetDateTime
 
 class FeedFragment : BaseListFragment<FeedState, Unit>() {
     private var _feedBinding: FragmentFeedBinding? = null
@@ -58,7 +58,7 @@ class FeedFragment : BaseListFragment<FeedState, Unit>() {
 
     private var groupId = FeedGroupEntity.GROUP_ALL_ID
     private var groupName = ""
-    private var oldestSubscriptionUpdate: Calendar? = null
+    private var oldestSubscriptionUpdate: OffsetDateTime? = null
 
     init {
         setHasOptionsMenu(true)
@@ -275,12 +275,10 @@ class FeedFragment : BaseListFragment<FeedState, Unit>() {
     }
 
     private fun updateRefreshViewState() {
-        val oldestSubscriptionUpdateText = when {
-            oldestSubscriptionUpdate != null -> Localization.relativeTime(oldestSubscriptionUpdate!!)
-            else -> "—"
-        }
-
-        feedBinding.refreshText.text = getString(R.string.feed_oldest_subscription_update, oldestSubscriptionUpdateText)
+        feedBinding.refreshText.text = getString(
+            R.string.feed_oldest_subscription_update,
+            oldestSubscriptionUpdate?.let { Localization.relativeTime(it) } ?: "—"
+        )
     }
 
     // /////////////////////////////////////////////////////////////////////////

app/src/main/java/org/schabi/newpipe/local/feed/FeedState.kt

@@ -2,7 +2,7 @@ package org.schabi.newpipe.local.feed
 
 import androidx.annotation.StringRes
 import org.schabi.newpipe.extractor.stream.StreamInfoItem
-import java.util.Calendar
+import java.time.OffsetDateTime
 
 sealed class FeedState {
     data class ProgressState(
@@ -13,7 +13,7 @@ sealed class FeedState {
 
     data class LoadedState(
         val items: List<StreamInfoItem>,
-        val oldestUpdate: Calendar? = null,
+        val oldestUpdate: OffsetDateTime? = null,
         val notLoadedCount: Long,
         val itemsErrors: List<Throwable> = emptyList()
     ) : FeedState()

app/src/main/java/org/schabi/newpipe/local/feed/FeedViewModel.kt

@@ -11,7 +11,6 @@ import io.reactivex.rxjava3.functions.Function4
 import io.reactivex.rxjava3.schedulers.Schedulers
 import org.schabi.newpipe.database.feed.model.FeedGroupEntity
 import org.schabi.newpipe.extractor.stream.StreamInfoItem
-import org.schabi.newpipe.ktx.toCalendar
 import org.schabi.newpipe.local.feed.service.FeedEventManager
 import org.schabi.newpipe.local.feed.service.FeedEventManager.Event.ErrorResultEvent
 import org.schabi.newpipe.local.feed.service.FeedEventManager.Event.IdleEvent
@@ -48,13 +47,11 @@ class FeedViewModel(applicationContext: Context, val groupId: Long = FeedGroupEn
         .subscribeOn(Schedulers.io())
         .observeOn(AndroidSchedulers.mainThread())
         .subscribe { (event, listFromDB, notLoadedCount, oldestUpdate) ->
-            val oldestUpdateCalendar = oldestUpdate?.toCalendar()
-
             mutableStateLiveData.postValue(
                 when (event) {
-                    is IdleEvent -> FeedState.LoadedState(listFromDB, oldestUpdateCalendar, notLoadedCount)
+                    is IdleEvent -> FeedState.LoadedState(listFromDB, oldestUpdate, notLoadedCount)
                     is ProgressEvent -> FeedState.ProgressState(event.currentProgress, event.maxProgress, event.progressMessage)
-                    is SuccessResultEvent -> FeedState.LoadedState(listFromDB, oldestUpdateCalendar, notLoadedCount, event.itemsErrors)
+                    is SuccessResultEvent -> FeedState.LoadedState(listFromDB, oldestUpdate, notLoadedCount, event.itemsErrors)
                     is ErrorResultEvent -> FeedState.ErrorState(event.error)
                 }
             )

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

@@ -20,7 +20,6 @@ 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 +29,6 @@ import java.time.ZoneId;
 import java.time.format.DateTimeFormatter;
 import java.time.format.FormatStyle;
 import java.util.Arrays;
-import java.util.Calendar;
 import java.util.List;
 import java.util.Locale;
 
@@ -314,11 +312,7 @@ public final class Localization {
     }
 
     public static String relativeTime(final OffsetDateTime offsetDateTime) {
-        return relativeTime(OffsetDateTimeKt.toCalendar(offsetDateTime));
-    }
-
-    public static String relativeTime(final Calendar calendarTime) {
-        return prettyTime.formatUnrounded(calendarTime);
+        return prettyTime.formatUnrounded(offsetDateTime);
     }
 
     private static void changeAppLanguage(final Locale loc, final Resources res) {