diff --git a/README.md b/README.md
index 4f4b2cad..063a852d 100644
--- a/README.md
+++ b/README.md
@@ -161,13 +161,14 @@ Here are some examples of conditions you can use:
 
 #### Placeholders
 
-| Placeholder             | Description                                             | Example of resolved value |
-|:----------------------- |:------------------------------------------------------- |:------------------------- |
-| `[STATUS]`              | Resolves into the HTTP status of the request            | 404
-| `[RESPONSE_TIME]`       | Resolves into the response time the request took, in ms | 10
-| `[IP]`                  | Resolves into the IP of the target host                 | 192.168.0.232
-| `[BODY]`                | Resolves into the response body. Supports JSONPath.     | `{"name":"john.doe"}`
-| `[CONNECTED]`           | Resolves into whether a connection could be established | `true`
+| Placeholder                | Description                                                     | Example of resolved value |
+|:-------------------------- |:--------------------------------------------------------------- |:------------------------- |
+| `[STATUS]`                 | Resolves into the HTTP status of the request                    | 404
+| `[RESPONSE_TIME]`          | Resolves into the response time the request took, in ms         | 10
+| `[IP]`                     | Resolves into the IP of the target host                         | 192.168.0.232
+| `[BODY]`                   | Resolves into the response body. Supports JSONPath.             | `{"name":"john.doe"}`
+| `[CONNECTED]`              | Resolves into whether a connection could be established         | `true`
+| `[CERTIFICATE_EXPIRATION]` | Resolves into the duration before certificate expiration, in ms | 4461677039, 0 (if not using HTTPS)
 
 
 #### Functions
diff --git a/core/condition.go b/core/condition.go
index ec2c7931..964416fd 100644
--- a/core/condition.go
+++ b/core/condition.go
@@ -35,6 +35,11 @@ const (
 	// Values that could replace the placeholder: true, false
 	ConnectedPlaceHolder = "[CONNECTED]"
 
+	// CertificateExpirationPlaceholder is a placeholder for the duration before certificate expiration, in milliseconds.
+	//
+	// Values that could replace the placeholder: 4461677039 (~52 days)
+	CertificateExpirationPlaceholder = "[CERTIFICATE_EXPIRATION]"
+
 	// LengthFunctionPrefix is the prefix for the length function
 	LengthFunctionPrefix = "len("
 
@@ -142,6 +147,8 @@ func sanitizeAndResolve(list []string, result *Result) []string {
 			element = body
 		case ConnectedPlaceHolder:
 			element = strconv.FormatBool(result.Connected)
+		case CertificateExpirationPlaceholder:
+			element = strconv.FormatInt(int64(result.CertificateExpiration.Milliseconds()), 10)
 		default:
 			// if contains the BodyPlaceHolder, then evaluate json path
 			if strings.Contains(element, BodyPlaceHolder) {
@@ -174,11 +181,11 @@ func sanitizeAndResolve(list []string, result *Result) []string {
 	return sanitizedList
 }
 
-func sanitizeAndResolveNumerical(list []string, result *Result) []int {
-	var sanitizedNumbers []int
+func sanitizeAndResolveNumerical(list []string, result *Result) []int64 {
+	var sanitizedNumbers []int64
 	sanitizedList := sanitizeAndResolve(list, result)
 	for _, element := range sanitizedList {
-		if number, err := strconv.Atoi(element); err != nil {
+		if number, err := strconv.ParseInt(element, 10, 64); err != nil {
 			// Default to 0 if the string couldn't be converted to an integer
 			sanitizedNumbers = append(sanitizedNumbers, 0)
 		} else {
diff --git a/core/condition_test.go b/core/condition_test.go
index 5ec95e25..d4e929df 100644
--- a/core/condition_test.go
+++ b/core/condition_test.go
@@ -1,6 +1,7 @@
 package core
 
 import (
+	"strconv"
 	"testing"
 	"time"
 )
@@ -309,3 +310,32 @@ func TestCondition_evaluateWithConnectedFailure(t *testing.T) {
 		t.Errorf("Condition '%s' should have been a failure", condition)
 	}
 }
+
+func TestCondition_evaluateWithUnsetCertificateExpiration(t *testing.T) {
+	condition := Condition("[CERTIFICATE_EXPIRATION] == 0")
+	result := &Result{}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithCertificateExpirationGreaterThan(t *testing.T) {
+	acceptable := (time.Hour * 24 * 28).Milliseconds()
+	condition := Condition("[CERTIFICATE_EXPIRATION] > " + strconv.FormatInt(acceptable, 10))
+	result := &Result{CertificateExpiration: time.Hour * 24 * 60}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithCertificateExpirationGreaterThanFailure(t *testing.T) {
+	acceptable := (time.Hour * 24 * 28).Milliseconds()
+	condition := Condition("[CERTIFICATE_EXPIRATION] > " + strconv.FormatInt(acceptable, 10))
+	result := &Result{CertificateExpiration: time.Hour * 24 * 14}
+	condition.evaluate(result)
+	if result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a failure", condition)
+	}
+}
diff --git a/core/service.go b/core/service.go
index 54bccfa5..0a025d8a 100644
--- a/core/service.go
+++ b/core/service.go
@@ -169,6 +169,10 @@ func (service *Service) call(result *Result) {
 			result.Errors = append(result.Errors, err.Error())
 			return
 		}
+		if response.TLS != nil {
+			certificate := response.TLS.PeerCertificates[0]
+			result.CertificateExpiration = certificate.NotAfter.Sub(time.Now())
+		}
 		result.HTTPStatus = response.StatusCode
 		result.Connected = response.StatusCode > 0
 		result.Body, err = ioutil.ReadAll(response.Body)
diff --git a/core/types.go b/core/types.go
index f17dbf3e..630c5df7 100644
--- a/core/types.go
+++ b/core/types.go
@@ -45,6 +45,9 @@ type Result struct {
 
 	// Timestamp when the request was sent
 	Timestamp time.Time `json:"timestamp"`
+
+	// CertificateExpiration is the duration before the certificate expires
+	CertificateExpiration time.Duration `json:"certificate-expiration,omitempty"`
 }
 
 // ConditionResult result of a Condition