diff --git a/aws/resource_aws_dlm_lifecycle_policy.go b/aws/resource_aws_dlm_lifecycle_policy.go
index 8b4f1e305bd..8a1c69f058c 100644
--- a/aws/resource_aws_dlm_lifecycle_policy.go
+++ b/aws/resource_aws_dlm_lifecycle_policy.go
@@ -106,9 +106,29 @@ func resourceAwsDlmLifecyclePolicy() *schema.Resource {
 											Schema: map[string]*schema.Schema{
 												"count": {
 													Type:         schema.TypeInt,
-													Required:     true,
+													Optional:     true,
+													ForceNew:     true,
 													ValidateFunc: validation.IntBetween(1, 1000),
 												},
+												"interval": {
+													Type:         schema.TypeInt,
+													Optional:     true,
+													ForceNew:     true,
+													Computed:     true,
+													ValidateFunc: validation.IntAtLeast(1),
+												},
+												"interval_unit": {
+													Type:     schema.TypeString,
+													Optional: true,
+													ForceNew: true,
+													Computed: true,
+													ValidateFunc: validation.StringInSlice([]string{
+														dlm.RetentionIntervalUnitValuesDays,
+														dlm.RetentionIntervalUnitValuesWeeks,
+														dlm.RetentionIntervalUnitValuesMonths,
+														dlm.RetentionIntervalUnitValuesYears,
+													}, false),
+												},
 											},
 										},
 									},
@@ -347,6 +367,7 @@ func flattenDlmCreateRule(createRule *dlm.CreateRule) []map[string]interface{} {
 	}
 
 	result := make(map[string]interface{})
+
 	result["interval"] = aws.Int64Value(createRule.Interval)
 	result["interval_unit"] = aws.StringValue(createRule.IntervalUnit)
 	result["times"] = flattenStringList(createRule.Times)
@@ -359,14 +380,34 @@ func expandDlmRetainRule(cfg []interface{}) *dlm.RetainRule {
 		return nil
 	}
 	m := cfg[0].(map[string]interface{})
-	return &dlm.RetainRule{
-		Count: aws.Int64(int64(m["count"].(int))),
+
+	retainRule := &dlm.RetainRule{}
+
+	if v := m["count"]; v.(int) > 0 {
+		retainRule.Count = aws.Int64(int64(v.(int)))
 	}
+
+	if v := m["interval"]; v.(int) > 0 {
+		retainRule.Interval = aws.Int64(int64(v.(int)))
+	}
+
+	if v, ok := m["interval_unit"]; ok {
+		retainRule.IntervalUnit = aws.String(v.(string))
+	}
+
+	return retainRule
 }
 
 func flattenDlmRetainRule(retainRule *dlm.RetainRule) []map[string]interface{} {
 	result := make(map[string]interface{})
-	result["count"] = aws.Int64Value(retainRule.Count)
+
+	if aws.Int64Value(retainRule.Count) > int64(0) {
+		result["count"] = aws.Int64Value(retainRule.Count)
+	}
+	if aws.Int64Value(retainRule.Interval) != 0 {
+		result["interval"] = aws.Int64Value(retainRule.Interval)
+	}
+	result["interval_unit"] = aws.StringValue(retainRule.IntervalUnit)
 
 	return []map[string]interface{}{result}
 }
diff --git a/aws/resource_aws_dlm_lifecycle_policy_test.go b/aws/resource_aws_dlm_lifecycle_policy_test.go
index 10b84f5be56..e736f7c4272 100644
--- a/aws/resource_aws_dlm_lifecycle_policy_test.go
+++ b/aws/resource_aws_dlm_lifecycle_policy_test.go
@@ -97,6 +97,44 @@ func TestAccAWSDlmLifecyclePolicy_Full(t *testing.T) {
 	})
 }
 
+func TestAccAWSDlmLifecyclePolicy_Retain(t *testing.T) {
+	resourceName := "aws_dlm_lifecycle_policy.full"
+	rName := acctest.RandomWithPrefix("tf-acc-test")
+
+	resource.ParallelTest(t, resource.TestCase{
+		PreCheck:     func() { testAccPreCheck(t); testAccPreCheckAWSDlm(t) },
+		Providers:    testAccProviders,
+		CheckDestroy: dlmLifecyclePolicyDestroy,
+		Steps: []resource.TestStep{
+			{
+				Config: dlmLifecyclePolicyFullUpdateConfigWithAgeBasedRetain(rName),
+				Check: resource.ComposeTestCheckFunc(
+					checkDlmLifecyclePolicyExists(resourceName),
+					resource.TestCheckResourceAttr(resourceName, "description", "tf-acc-full-updated-age"),
+					resource.TestCheckResourceAttrSet(resourceName, "execution_role_arn"),
+					resource.TestCheckResourceAttr(resourceName, "state", "DISABLED"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.resource_types.0", "VOLUME"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.schedule.0.name", "tf-acc-full-updated-age"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.schedule.0.create_rule.0.interval", "24"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.schedule.0.create_rule.0.interval_unit", "HOURS"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.schedule.0.create_rule.0.times.0", "09:42"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.schedule.0.retain_rule.0.interval", "15"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.schedule.0.retain_rule.0.interval_unit", "DAYS"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.schedule.0.tags_to_add.tf-acc-test-added", "full-updated-age"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.schedule.0.copy_tags", "true"),
+					resource.TestCheckResourceAttr(resourceName, "policy_details.0.target_tags.tf-acc-test", "full-updated-age"),
+				),
+			},
+			{
+				Config: dlmLifecyclePolicyFullUpdateConfigWithAgeBasedRetainless(rName),
+				Check: resource.ComposeTestCheckFunc(
+					checkDlmLifecyclePolicyExists(resourceName),
+				),
+			},
+		},
+	})
+}
+
 func TestAccAWSDlmLifecyclePolicy_Tags(t *testing.T) {
 	rName := acctest.RandomWithPrefix("tf-acc-test")
 	resourceName := "aws_dlm_lifecycle_policy.test"
@@ -246,7 +284,7 @@ resource "aws_dlm_lifecycle_policy" "basic" {
       }
 
       retain_rule {
-        count = 10
+        count         = 10
       }
     }
 
@@ -374,6 +412,123 @@ resource "aws_dlm_lifecycle_policy" "full" {
 `, rName)
 }
 
+func dlmLifecyclePolicyFullUpdateConfigWithAgeBasedRetain(rName string) string {
+	return fmt.Sprintf(`
+resource "aws_iam_role" "dlm_lifecycle_role" {
+  name = %q
+
+  assume_role_policy = <<EOF
+{
+  "Version": "2012-10-17",
+  "Statement": [
+    {
+      "Action": "sts:AssumeRole",
+      "Principal": {
+        "Service": "dlm.amazonaws.com"
+      },
+      "Effect": "Allow",
+      "Sid": ""
+    }
+  ]
+}
+EOF
+}
+
+resource "aws_dlm_lifecycle_policy" "full" {
+  description        = "tf-acc-full-updated-age"
+  execution_role_arn = "${aws_iam_role.dlm_lifecycle_role.arn}-doesnt-exist"
+  state              = "DISABLED"
+
+  policy_details {
+    resource_types = ["VOLUME"]
+
+    schedule {
+      name = "tf-acc-full-updated-age"
+
+      create_rule {
+        interval      = 24
+        interval_unit = "HOURS"
+        times         = ["09:42"]
+      }
+
+      retain_rule {
+				interval			= 15
+				interval_unit = "DAYS"
+      }
+
+      tags_to_add = {
+        tf-acc-test-added = "full-updated-age"
+      }
+
+      copy_tags = true
+    }
+
+    target_tags = {
+      tf-acc-test = "full-updated-age"
+    }
+  }
+}
+`, rName)
+}
+
+func dlmLifecyclePolicyFullUpdateConfigWithAgeBasedRetainless(rName string) string {
+	return fmt.Sprintf(`
+resource "aws_iam_role" "dlm_lifecycle_role" {
+  name = %q
+
+  assume_role_policy = <<EOF
+{
+  "Version": "2012-10-17",
+  "Statement": [
+    {
+      "Action": "sts:AssumeRole",
+      "Principal": {
+        "Service": "dlm.amazonaws.com"
+      },
+      "Effect": "Allow",
+      "Sid": ""
+    }
+  ]
+}
+EOF
+}
+
+resource "aws_dlm_lifecycle_policy" "full" {
+  description        = "tf-acc-full-updated-age"
+  execution_role_arn = "${aws_iam_role.dlm_lifecycle_role.arn}-doesnt-exist"
+  state              = "DISABLED"
+
+  policy_details {
+    resource_types = ["VOLUME"]
+
+    schedule {
+      name = "tf-acc-full-updated-age"
+
+      create_rule {
+        interval      = 24
+        interval_unit = "HOURS"
+        times         = ["09:42"]
+      }
+
+      retain_rule {
+			  count = 5
+      }
+
+      tags_to_add = {
+        tf-acc-test-added = "full-updated-age"
+      }
+
+      copy_tags = true
+    }
+
+    target_tags = {
+      tf-acc-test = "full-updated-age"
+    }
+  }
+}
+`, rName)
+}
+
 func dlmLifecyclePolicyConfigTags1(rName, tagKey1, tagValue1 string) string {
 	return fmt.Sprintf(`
 resource "aws_iam_role" "test" {
diff --git a/website/docs/r/dlm_lifecycle_policy.markdown b/website/docs/r/dlm_lifecycle_policy.markdown
index e5157107c68..ceeba280553 100644
--- a/website/docs/r/dlm_lifecycle_policy.markdown
+++ b/website/docs/r/dlm_lifecycle_policy.markdown
@@ -121,7 +121,7 @@ The following arguments are supported:
 * `copy_tags` - (Optional) Copy all user-defined tags on a source volume to snapshots of the volume created by this policy.
 * `create_rule` - (Required) See the [`create_rule`](#create-rule-arguments) block. Max of 1 per schedule.
 * `name` - (Required) A name for the schedule.
-* `retain_rule` - (Required) See the [`retain_rule`](#retain-rule-arguments) block. Max of 1 per schedule.
+* `retain_rule` - (Required) See the [`retain_rule`](#retain-rule-arguments) block.
 * `tags_to_add` - (Optional) A mapping of tag keys and their values. DLM lifecycle policies will already tag the snapshot with the tags on the volume. This configuration adds extra tags on top of these.
 
 #### Create Rule arguments
@@ -132,7 +132,11 @@ The following arguments are supported:
 
 #### Retain Rule arguments
 
-* `count` - (Required) How many snapshots to keep. Must be an integer between 1 and 1000.
+Note: One of either `count` or `interval`/`interval_unit` must be specified.
+
+* `count` - (Optional) How many snapshots to keep. Must be an integer between 1 and 1000. 
+* `interval` - (Optional) The amount of time to retain each snapshot. The maximum is 100 years or that equivalent in months (1200), weeks (5200), and days (36500).
+* `interval_unit` - (Optional) The unit of time for time-based retention.
 
 ## Attributes Reference