AutoDateHistogramAggregate Interval should be DateMathTime

src/Nest/Aggregations/AggregateFormatter.cs

@@ -665,7 +665,7 @@ private IAggregate GetMultiBucketAggregate(ref JsonReader reader, IJsonFormatter
 				reader.ReadNext();
 				propertyName = reader.ReadPropertyNameSegmentRaw();
 				if (propertyName.EqualsBytes(JsonWriter.GetEncodedPropertyNameWithoutQuotation("interval")))
-					bucket.Interval = formatterResolver.GetFormatter<Time>().Deserialize(ref reader, formatterResolver);
+					bucket.Interval = formatterResolver.GetFormatter<DateMathTime>().Deserialize(ref reader, formatterResolver);
 				else
 					// skip for now
 					reader.ReadNextBlock();

src/Nest/Aggregations/Bucket/AutoDateHistogram/AutoDateHistogramBucket.cs

@@ -6,6 +6,6 @@
 {
 	public class AutoDateHistogramAggregate : MultiBucketAggregate<DateHistogramBucket>
 	{
-		public Time Interval { get; internal set; }
+		public DateMathTime Interval { get; internal set; }
 	}
 }

src/Nest/Aggregations/Bucket/BucketAggregate.cs

@@ -68,6 +68,6 @@ public class BucketAggregate : IAggregate
 		public IReadOnlyCollection<IBucket> Items { get; set; } = EmptyReadOnly<IBucket>.Collection;
 		public IReadOnlyDictionary<string, object> Meta { get; set; } = EmptyReadOnly<string, object>.Dictionary;
 		public long? SumOtherDocCount { get; set; }
-		public Time Interval { get; set; }
+		public DateMathTime Interval { get; set; }
 	}
 }

tests/Tests.Reproduce/GitHubIssue4333.cs

@@ -0,0 +1,95 @@
+// Licensed to Elasticsearch B.V under one or more agreements.
+// Elasticsearch B.V licenses this file to you under the Apache 2.0 License.
+// See the LICENSE file in the project root for more information
+
+using System;
+using System.Text;
+using Elastic.Elasticsearch.Xunit.XunitPlumbing;
+using Elasticsearch.Net;
+using FluentAssertions;
+using Nest;
+
+namespace Tests.Reproduce
+{
+	public class GitHubIssue4333
+	{
+		[U]
+		public void CanDeserializeYearIntervalUnit()
+		{
+			var json = @"{
+			""took"" : 162,
+			""timed_out"" : false,
+			""_shards"" : {
+				""total"" : 3,
+				""successful"" : 3,
+				""skipped"" : 0,
+				""failed"" : 0
+			},
+			""hits"" : {
+				""total"" : 4089559,
+				""max_score"" : 0.0,
+				""hits"" : [ ]
+			},
+			""aggregations"" : {
+				""modDate"" : {
+					""buckets"" : [
+					{
+						""key_as_string"" : ""2013-01-01T00:00:00.000Z"",
+						""key"" : 1356998400000,
+						""doc_count"" : 32
+					},
+					{
+						""key_as_string"" : ""2014-01-01T00:00:00.000Z"",
+						""key"" : 1388534400000,
+						""doc_count"" : 617
+					},
+					{
+						""key_as_string"" : ""2015-01-01T00:00:00.000Z"",
+						""key"" : 1420070400000,
+						""doc_count"" : 183
+					},
+					{
+						""key_as_string"" : ""2016-01-01T00:00:00.000Z"",
+						""key"" : 1451606400000,
+						""doc_count"" : 3479
+					},
+					{
+						""key_as_string"" : ""2017-01-01T00:00:00.000Z"",
+						""key"" : 1483228800000,
+						""doc_count"" : 1948427
+					},
+					{
+						""key_as_string"" : ""2018-01-01T00:00:00.000Z"",
+						""key"" : 1514764800000,
+						""doc_count"" : 555748
+					},
+					{
+						""key_as_string"" : ""2019-01-01T00:00:00.000Z"",
+						""key"" : 1546300800000,
+						""doc_count"" : 1268034
+					},
+					{
+						""key_as_string"" : ""2020-01-01T00:00:00.000Z"",
+						""key"" : 1577836800000,
+						""doc_count"" : 313039
+					}
+					],
+					""interval"" : ""1y""
+				}
+			}
+		}";
+
+			var bytes = Encoding.UTF8.GetBytes(json);
+			var pool = new SingleNodeConnectionPool(new Uri("http://localhost:9200"));
+			var connectionSettings = new ConnectionSettings(pool, new InMemoryConnection(bytes)).DefaultIndex("default_index");
+			var client = new ElasticClient(connectionSettings);
+
+			var response = client.Search<object>();
+
+			Func<AutoDateHistogramAggregate> func = () => response.Aggregations.AutoDateHistogram("modDate");
+
+			var agg = func.Should().NotThrow().Subject;
+			agg.Interval.Should().Be("1y");
+		}
+	}
+}