Change timestamp format. Ensure we always have a date break between messages on different days.

Signal/src/ViewControllers/ConversationView/Cells/OWSMessageFooterView.m

@@ -147,7 +147,7 @@ NS_ASSUME_NONNULL_BEGIN
 
     [self configureFonts];
 
-    self.timestampLabel.text = [DateUtil formatTimestampShort:viewItem.interaction.timestamp];
+    self.timestampLabel.text = [DateUtil formatTimestampAsTimeShort:viewItem.interaction.timestamp];
 }
 
 - (CGSize)measureWithConversationViewItem:(ConversationViewItem *)viewItem

Signal/src/ViewControllers/ConversationView/ConversationViewController.m

@@ -4823,6 +4823,9 @@ typedef enum : NSUInteger {
                 break;
         }
 
+        uint64_t viewItemTimestamp = viewItem.interaction.timestampForSorting;
+        OWSAssert(viewItemTimestamp > 0);
+
         BOOL shouldShowDate = NO;
         if (!canShowDate) {
             shouldShowDate = NO;
@@ -4830,9 +4833,12 @@ typedef enum : NSUInteger {
         } else if (shouldShowDateOnNextViewItem) {
             shouldShowDate = YES;
             shouldShowDateOnNextViewItem = NO;
+        } else if (previousViewItemTimestamp > 0
+            && ![DateUtil isSameDayWithTimestamp:previousViewItemTimestamp timestamp:viewItemTimestamp]) {
+            // Ensure we always have a date break between messages on different days.
+            shouldShowDate = YES;
+            shouldShowDateOnNextViewItem = NO;
         } else {
-            uint64_t viewItemTimestamp = viewItem.interaction.timestampForSorting;
-            OWSAssert(viewItemTimestamp > 0);
             OWSAssert(previousViewItemTimestamp > 0);
             uint64_t timeDifferenceMs = viewItemTimestamp - previousViewItemTimestamp;
             static const uint64_t kShowTimeIntervalMs = 5 * kMinuteInMs;
@@ -4844,7 +4850,7 @@ typedef enum : NSUInteger {
 
         viewItem.shouldShowDate = shouldShowDate;
 
-        previousViewItemTimestamp = viewItem.interaction.timestampForSorting;
+        previousViewItemTimestamp = viewItemTimestamp;
     }
 
     // Update the properties of the view items.

Signal/src/util/DateUtil.h

@@ -23,6 +23,12 @@ NS_ASSUME_NONNULL_BEGIN
 + (NSString *)formatTimestampShort:(uint64_t)timestamp;
 + (NSString *)formatDateShort:(NSDate *)date;
 
++ (NSString *)formatTimestampAsTimeShort:(uint64_t)timestamp;
++ (NSString *)formatDateAsTimeShort:(NSDate *)date;
+
++ (BOOL)isSameDayWithTimestamp:(uint64_t)timestamp1 timestamp:(uint64_t)timestamp2;
++ (BOOL)isSameDayWithDate:(NSDate *)date1 date:(NSDate *)date2;
+
 @end
 
 NS_ASSUME_NONNULL_END

Signal/src/util/DateUtil.m

@@ -187,6 +187,30 @@ static NSString *const DATE_FORMAT_WEEKDAY = @"EEEE";
     return dateTimeString.uppercaseString;
 }
 
++ (NSString *)formatTimestampAsTimeShort:(uint64_t)timestamp
+{
+    return [self formatDateAsTimeShort:[NSDate ows_dateWithMillisecondsSince1970:timestamp]];
+}
+
++ (NSString *)formatDateAsTimeShort:(NSDate *)date
+{
+    OWSAssert(date);
+
+    NSString *dateTimeString = [[DateUtil timeFormatter] stringFromDate:date];
+    return dateTimeString.uppercaseString;
+}
+
++ (BOOL)isSameDayWithTimestamp:(uint64_t)timestamp1 timestamp:(uint64_t)timestamp2
+{
+    return [self isSameDayWithDate:[NSDate ows_dateWithMillisecondsSince1970:timestamp1]
+                              date:[NSDate ows_dateWithMillisecondsSince1970:timestamp2]];
+}
+
++ (BOOL)isSameDayWithDate:(NSDate *)date1 date:(NSDate *)date2
+{
+    NSInteger dayDifference = [self daysFromFirstDate:date1 toSecondDate:date2];
+    return dayDifference == 0;
+}
 @end
 
 NS_ASSUME_NONNULL_END