diff --git a/.dockerignore b/.dockerignore
index c1f70b21..c7c11b97 100644
--- a/.dockerignore
+++ b/.dockerignore
@@ -1,3 +1,5 @@
 example
+Dockerfile
 .github
 .idea
+.git
diff --git a/Dockerfile b/Dockerfile
index d926f7c7..83bb78a3 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,9 +1,9 @@
 # Build the go application into a binary
 FROM golang:alpine as builder
-WORKDIR /app
-ADD . ./
-RUN CGO_ENABLED=0 GOOS=linux go build -mod vendor -a -installsuffix cgo -o gatus .
 RUN apk --update add ca-certificates
+WORKDIR /app
+COPY . ./
+RUN CGO_ENABLED=0 GOOS=linux go build -mod vendor -a -installsuffix cgo -o gatus .
 
 # Run Tests inside docker image if you don't have a configured go environment
 #RUN apk update && apk add --virtual build-dependencies build-base gcc
@@ -17,4 +17,4 @@ COPY --from=builder /app/static static/
 COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/ca-certificates.crt
 ENV PORT=8080
 EXPOSE ${PORT}
-ENTRYPOINT ["/gatus"]
\ No newline at end of file
+ENTRYPOINT ["/gatus"]
diff --git a/README.md b/README.md
index 8c82b70e..da1aec01 100644
--- a/README.md
+++ b/README.md
@@ -159,6 +159,7 @@ Here are some examples of conditions you can use:
 | `len([BODY].data) < 5`       | Array at JSONPath `$.data` has less than 5 elements     | `{"data":[{"id":1}]}`      |  |
 | `len([BODY].name) == 8`      | String at JSONPath `$.name` has a length of 8           | `{"name":"john.doe"}`      | `{"name":"bob"}` |
 | `[BODY].name == pat(john*)`  | String at JSONPath `$.name` matches pattern `john*`     | `{"name":"john.doe"}`      | `{"name":"bob"}` |
+| `[CERTIFICATE_EXPIRATION] > 48h` | Certificate expiration is more than 48h away        | 49h, 50h, 123h             | 1h, 24h, ... |
 
 
 #### Placeholders
@@ -171,7 +172,7 @@ Here are some examples of conditions you can use:
 | `[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)
+| `[CERTIFICATE_EXPIRATION]` | Resolves into the duration before certificate expiration        | `24h`, `48h`, 0 (if not using HTTPS)
 
 
 #### Functions
diff --git a/alerting/provider/slack/slack.go b/alerting/provider/slack/slack.go
index a7d1f153..2c613a58 100644
--- a/alerting/provider/slack/slack.go
+++ b/alerting/provider/slack/slack.go
@@ -2,6 +2,7 @@ package slack
 
 import (
 	"fmt"
+
 	"github.com/TwinProduction/gatus/alerting/provider/custom"
 	"github.com/TwinProduction/gatus/core"
 )
@@ -18,8 +19,7 @@ func (provider *AlertProvider) IsValid() bool {
 
 // ToCustomAlertProvider converts the provider into a custom.AlertProvider
 func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, alert *core.Alert, result *core.Result, resolved bool) *custom.AlertProvider {
-	var message string
-	var color string
+	var message, color, results string
 	if resolved {
 		message = fmt.Sprintf("An alert for *%s* has been resolved after passing successfully %d time(s) in a row", service.Name, alert.SuccessThreshold)
 		color = "#36A64F"
@@ -27,7 +27,6 @@ func (provider *AlertProvider) ToCustomAlertProvider(service *core.Service, aler
 		message = fmt.Sprintf("An alert for *%s* has been triggered due to having failed %d time(s) in a row", service.Name, alert.FailureThreshold)
 		color = "#DD0000"
 	}
-	var results string
 	for _, conditionResult := range result.ConditionResults {
 		var prefix string
 		if conditionResult.Success {
diff --git a/alerting/provider/slack/slack_test.go b/alerting/provider/slack/slack_test.go
index 9b853d5b..4f1c8d2d 100644
--- a/alerting/provider/slack/slack_test.go
+++ b/alerting/provider/slack/slack_test.go
@@ -1,9 +1,10 @@
 package slack
 
 import (
-	"github.com/TwinProduction/gatus/core"
 	"strings"
 	"testing"
+
+	"github.com/TwinProduction/gatus/core"
 )
 
 func TestAlertProvider_IsValid(t *testing.T) {
diff --git a/core/condition.go b/core/condition.go
index 792b788a..220b9307 100644
--- a/core/condition.go
+++ b/core/condition.go
@@ -2,11 +2,13 @@ package core
 
 import (
 	"fmt"
-	"github.com/TwinProduction/gatus/jsonpath"
-	"github.com/TwinProduction/gatus/pattern"
 	"log"
 	"strconv"
 	"strings"
+	"time"
+
+	"github.com/TwinProduction/gatus/jsonpath"
+	"github.com/TwinProduction/gatus/pattern"
 )
 
 const (
@@ -15,30 +17,30 @@ const (
 	// Values that could replace the placeholder: 200, 404, 500, ...
 	StatusPlaceholder = "[STATUS]"
 
-	// IPPlaceHolder is a placeholder for an IP.
+	// IPPlaceholder is a placeholder for an IP.
 	//
 	// Values that could replace the placeholder: 127.0.0.1, 10.0.0.1, ...
-	IPPlaceHolder = "[IP]"
+	IPPlaceholder = "[IP]"
 
 	// DNSRCodePlaceHolder is a place holder for DNS_RCODE
 	//
 	// Values that could be NOERROR, FORMERR, SERVFAIL, NXDOMAIN, NOTIMP and REFUSED
 	DNSRCodePlaceHolder = "[DNS_RCODE]"
 
-	// ResponseTimePlaceHolder is a placeholder for the request response time, in milliseconds.
+	// ResponseTimePlaceholder is a placeholder for the request response time, in milliseconds.
 	//
 	// Values that could replace the placeholder: 1, 500, 1000, ...
-	ResponseTimePlaceHolder = "[RESPONSE_TIME]"
+	ResponseTimePlaceholder = "[RESPONSE_TIME]"
 
-	// BodyPlaceHolder is a placeholder for the body of the response
+	// BodyPlaceholder is a placeholder for the body of the response
 	//
 	// Values that could replace the placeholder: {}, {"data":{"name":"john"}}, ...
-	BodyPlaceHolder = "[BODY]"
+	BodyPlaceholder = "[BODY]"
 
-	// ConnectedPlaceHolder is a placeholder for whether a connection was successfully established.
+	// ConnectedPlaceholder is a placeholder for whether a connection was successfully established.
 	//
 	// Values that could replace the placeholder: true, false
-	ConnectedPlaceHolder = "[CONNECTED]"
+	ConnectedPlaceholder = "[CONNECTED]"
 
 	// CertificateExpirationPlaceholder is a placeholder for the duration before certificate expiration, in milliseconds.
 	//
@@ -144,27 +146,27 @@ func sanitizeAndResolve(list []string, result *Result) []string {
 		switch strings.ToUpper(element) {
 		case StatusPlaceholder:
 			element = strconv.Itoa(result.HTTPStatus)
-		case IPPlaceHolder:
+		case IPPlaceholder:
 			element = result.IP
-		case ResponseTimePlaceHolder:
+		case ResponseTimePlaceholder:
 			element = strconv.Itoa(int(result.Duration.Milliseconds()))
+		case BodyPlaceholder:
+			element = body
 		case DNSRCodePlaceHolder:
 			element = result.DNSRCode
-		case BodyPlaceHolder:
-			element = body
-		case ConnectedPlaceHolder:
+		case ConnectedPlaceholder:
 			element = strconv.FormatBool(result.Connected)
 		case CertificateExpirationPlaceholder:
-			element = strconv.FormatInt(int64(result.CertificateExpiration.Milliseconds()), 10)
+			element = strconv.FormatInt(result.CertificateExpiration.Milliseconds(), 10)
 		default:
-			// if contains the BodyPlaceHolder, then evaluate json path
-			if strings.Contains(element, BodyPlaceHolder) {
+			// if contains the BodyPlaceholder, then evaluate json path
+			if strings.Contains(element, BodyPlaceholder) {
 				wantLength := false
 				if strings.HasPrefix(element, LengthFunctionPrefix) && strings.HasSuffix(element, FunctionSuffix) {
 					wantLength = true
 					element = strings.TrimSuffix(strings.TrimPrefix(element, LengthFunctionPrefix), FunctionSuffix)
 				}
-				resolvedElement, resolvedElementLength, err := jsonpath.Eval(strings.Replace(element, fmt.Sprintf("%s.", BodyPlaceHolder), "", 1), result.Body)
+				resolvedElement, resolvedElementLength, err := jsonpath.Eval(strings.Replace(element, fmt.Sprintf("%s.", BodyPlaceholder), "", 1), result.Body)
 				if err != nil {
 					if err.Error() != "unexpected end of JSON input" {
 						result.Errors = append(result.Errors, err.Error())
@@ -192,7 +194,9 @@ func sanitizeAndResolveNumerical(list []string, result *Result) []int64 {
 	var sanitizedNumbers []int64
 	sanitizedList := sanitizeAndResolve(list, result)
 	for _, element := range sanitizedList {
-		if number, err := strconv.ParseInt(element, 10, 64); err != nil {
+		if duration, err := time.ParseDuration(element); duration != 0 && err == nil {
+			sanitizedNumbers = append(sanitizedNumbers, duration.Milliseconds())
+		} else 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 d4e929df..3aa3fc6d 100644
--- a/core/condition_test.go
+++ b/core/condition_test.go
@@ -60,7 +60,27 @@ func TestCondition_evaluateWithResponseTimeUsingLessThan(t *testing.T) {
 	}
 }
 
+func TestCondition_evaluateWithResponseTimeUsingLessThanDuration(t *testing.T) {
+	condition := Condition("[RESPONSE_TIME] < 1s")
+	result := &Result{Duration: time.Millisecond * 50}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithResponseTimeUsingLessThanInvalid(t *testing.T) {
+	condition := Condition("[RESPONSE_TIME] < potato")
+	result := &Result{Duration: time.Millisecond * 50}
+	condition.evaluate(result)
+	if result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have failed because the condition has an invalid numerical value that should've automatically resolved to 0", condition)
+	}
+}
+
 func TestCondition_evaluateWithResponseTimeUsingGreaterThan(t *testing.T) {
+	// Not exactly sure why you'd want to have a condition that checks if the response time is too fast,
+	// but hey, who am I to judge?
 	condition := Condition("[RESPONSE_TIME] > 500")
 	result := &Result{Duration: time.Millisecond * 750}
 	condition.evaluate(result)
@@ -69,6 +89,15 @@ func TestCondition_evaluateWithResponseTimeUsingGreaterThan(t *testing.T) {
 	}
 }
 
+func TestCondition_evaluateWithResponseTimeUsingGreaterThanDuration(t *testing.T) {
+	condition := Condition("[RESPONSE_TIME] > 1s")
+	result := &Result{Duration: time.Second * 2}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
 func TestCondition_evaluateWithResponseTimeUsingGreaterThanOrEqualTo(t *testing.T) {
 	condition := Condition("[RESPONSE_TIME] >= 500")
 	result := &Result{Duration: time.Millisecond * 500}
@@ -320,7 +349,7 @@ func TestCondition_evaluateWithUnsetCertificateExpiration(t *testing.T) {
 	}
 }
 
-func TestCondition_evaluateWithCertificateExpirationGreaterThan(t *testing.T) {
+func TestCondition_evaluateWithCertificateExpirationGreaterThanNumerical(t *testing.T) {
 	acceptable := (time.Hour * 24 * 28).Milliseconds()
 	condition := Condition("[CERTIFICATE_EXPIRATION] > " + strconv.FormatInt(acceptable, 10))
 	result := &Result{CertificateExpiration: time.Hour * 24 * 60}
@@ -330,7 +359,7 @@ func TestCondition_evaluateWithCertificateExpirationGreaterThan(t *testing.T) {
 	}
 }
 
-func TestCondition_evaluateWithCertificateExpirationGreaterThanFailure(t *testing.T) {
+func TestCondition_evaluateWithCertificateExpirationGreaterThanNumericalFailure(t *testing.T) {
 	acceptable := (time.Hour * 24 * 28).Milliseconds()
 	condition := Condition("[CERTIFICATE_EXPIRATION] > " + strconv.FormatInt(acceptable, 10))
 	result := &Result{CertificateExpiration: time.Hour * 24 * 14}
@@ -339,3 +368,21 @@ func TestCondition_evaluateWithCertificateExpirationGreaterThanFailure(t *testin
 		t.Errorf("Condition '%s' should have been a failure", condition)
 	}
 }
+
+func TestCondition_evaluateWithCertificateExpirationGreaterThanDuration(t *testing.T) {
+	condition := Condition("[CERTIFICATE_EXPIRATION] > 12h")
+	result := &Result{CertificateExpiration: 24 * time.Hour}
+	condition.evaluate(result)
+	if !result.ConditionResults[0].Success {
+		t.Errorf("Condition '%s' should have been a success", condition)
+	}
+}
+
+func TestCondition_evaluateWithCertificateExpirationGreaterThanDurationFailure(t *testing.T) {
+	condition := Condition("[CERTIFICATE_EXPIRATION] > 48h")
+	result := &Result{CertificateExpiration: 24 * time.Hour}
+	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 fcaf5519..3ed67ce0 100644
--- a/core/service.go
+++ b/core/service.go
@@ -184,7 +184,7 @@ func (service *Service) call(result *Result) {
 			result.Errors = append(result.Errors, err.Error())
 			return
 		}
-		if response.TLS != nil {
+		if response.TLS != nil && len(response.TLS.PeerCertificates) > 0 {
 			certificate := response.TLS.PeerCertificates[0]
 			result.CertificateExpiration = certificate.NotAfter.Sub(time.Now())
 		}