Show modification date for files older than 30 days

I've got many thousands of files in my Nextcloud, the vast
majority of which are way older than 30 days, so just displaying
"over 30 days" for the age of these files doesn't really get me
anywhere. Also, I'm not at all interested in the age of these
files ("1643 days", anyone). What this commit does is replace
the "over 30 days" message by the actual file modification date,
formatted according to the iOS locale settings.

iOSClient/Utility/CCUtility.m

@@ -557,7 +557,7 @@
 }
 
 #pragma --------------------------------------------------------------------------------------------
-#pragma mark ===== Varius =====
+#pragma mark ===== Various =====
 #pragma --------------------------------------------------------------------------------------------
 
 + (NSString *)getUserAgent
@@ -569,27 +569,30 @@
 
 + (NSString *)dateDiff:(NSDate *) convertedDate
 {
-    NSDateFormatter *df = [[NSDateFormatter alloc] init];
-    [df setFormatterBehavior:NSDateFormatterBehavior10_4];
-    [df setDateFormat:@"EEE, dd MMM yy HH:mm:ss VVVV"];
-    //NSDate *convertedDate = [df dateFromString:origDate];
-    //NSDate *convertedDate = [NSDate dateWithTimeIntervalSince1970:origDate];
     NSDate *todayDate = [NSDate date];
     double ti = [convertedDate timeIntervalSinceDate:todayDate];
     ti = ti * -1;
     if (ti < 60) {
+        // This minute
         return NSLocalizedString(@"_less_a_minute_", nil);
     } else if (ti < 3600) {
+        // This hour
         int diff = round(ti / 60);
         return [NSString stringWithFormat:NSLocalizedString(@"_minutes_ago_", nil), diff];
     } else if (ti < 86400) {
+        // This day
         int diff = round(ti / 60 / 60);
         return[NSString stringWithFormat:NSLocalizedString(@"_hours_ago_", nil), diff];
-    } else if (ti < 2629743) {
+    } else if (ti < 86400 * 30) {
+        // This month
         int diff = round(ti / 60 / 60 / 24);
         return[NSString stringWithFormat:NSLocalizedString(@"_days_ago_", nil), diff];
     } else {
-        return NSLocalizedString(@"_over_30_days_", nil);
+        // Older than one month
+        NSDateFormatter *df = [[NSDateFormatter alloc] init];
+        [df setFormatterBehavior:NSDateFormatterBehavior10_4];
+        [df setDateStyle:NSDateFormatterMediumStyle];
+        return [df stringFromDate:convertedDate];
     }
 }