diff --git a/README.md b/README.md
index 41731eb..19155ce 100644
--- a/README.md
+++ b/README.md
@@ -31,8 +31,9 @@ Parameters and examples of use.
 
 ### Parameters
 ```
--d --domain [target_domain] (required)
--o --output [output_file] (optional)
+-d --domain    [target_domain] (required)
+-o --output    [output_file]   (optional)
+-v --validonly                 (optional)
 ```
 
 ### Examples
@@ -42,6 +43,10 @@ $ python3 ctfr.py -d starbucks.com
 ```bash
 $ python3 ctfr.py -d facebook.com -o /home/shei/subdomains_fb.txt
 ```
+```bash
+$ python3 ctfr.py -d starbucks.com -v
+```
+
 
 ### With Docker
 I think it's a little bit crazy to use Docker for running such a little python script, but if you want to do it anyway, you can download [this lightweight (97.8MB) Docker image](https://hub.docker.com/r/johnpaulada/ctfr/) made by John Paulada.
diff --git a/ctfr.py b/ctfr.py
index 36a2ea1..9a217a8 100644
--- a/ctfr.py
+++ b/ctfr.py
@@ -9,6 +9,8 @@
 ## # LIBRARIES # ##
 import re
 import requests
+import datetime
+from dateutil.parser import parse
 
 ## # CONTEXT VARIABLES # ##
 version = 1.2
@@ -19,6 +21,7 @@ def parse_args():
 	import argparse
 	parser = argparse.ArgumentParser()
 	parser.add_argument('-d', '--domain', type=str, required=True, help="Target domain.")
+        parser.add_argument('-v', '--validonly', action='store_true', help="Only include valid certs.")
 	parser.add_argument('-o', '--output', type=str, help="Output file.")
 	return parser.parse_args()
 
@@ -50,6 +53,7 @@ def main():
 
 	subdomains = []
 	target = clear_url(args.domain)
+        validonly = args.validonly
 	output = args.output
 
 	req = requests.get("https://crt.sh/?q=%.{d}&output=json".format(d=target))
@@ -59,7 +63,14 @@ def main():
 		exit(1)
 
 	for (key,value) in enumerate(req.json()):
-		subdomains.append(value['name_value'])
+                not_before = parse(value['not_before'])
+                not_after = parse(value['not_after'])
+                now = datetime.datetime.now()
+                if validonly:
+                        if (not_before < now < not_after):
+                                subdomains.append(value['name_value'])
+                else:
+                        subdomains.append(value['name_value'])
 
 	
 	print("\n[!] ---- TARGET: {d} ---- [!] \n".format(d=target))