Grep(exclude) lines that have regex matching next line - regex

Question

I have a log file that I am trying to grep -v all the unnecessary information so I can see only useful information. I cannot seem to figure out how to exclude the date if the next line after is also a date.
What I have so far:
Fri Apr 7 01:11:01 PDT 2017
Upgrading certbot-auto 0.12.0 to 0.13.0...
Replacing certbot-auto...
Installation succeeded.
Sat Apr 8 01:11:01 PDT 2017
Sun Apr 9 01:11:01 PDT 2017
Mon Apr 10 01:11:01 PDT 2017
Tue Apr 11 01:11:01 PDT 2017
Wed Apr 12 01:11:01 PDT 2017
Thu Apr 13 01:11:01 PDT 2017
Fri Apr 14 01:11:01 PDT 2017
Sat Apr 15 01:11:01 PDT 2017
Sun Apr 16 01:11:01 PDT 2017
Mon Apr 17 01:11:01 PDT 2017
Tue Apr 18 01:11:01 PDT 2017
Wed Apr 19 01:11:01 PDT 2017
Thu Apr 20 01:11:01 PDT 2017
Fri Apr 21 01:11:01 PDT 2017
WARNING: unable to check for updates.
Sat Apr 22 01:11:01 PDT 2017
Sun Apr 23 01:11:01 PDT 2017
Mon Apr 24 01:11:01 PDT 2017
Tue Apr 25 01:11:01 PDT 2017
What I want:
Fri Apr 7 01:11:01 PDT 2017
Upgrading certbot-auto 0.12.0 to 0.13.0...
Replacing certbot-auto...
Installation succeeded.
Fri Apr 21 01:11:01 PDT 2017
WARNING: unable to check for updates.

Answer 1

Well I came up with this one. See if this one helps.
Regex: ([A-Za-z]{3}\s[A-Za-z]{3}\s*\d{1,2}\s(?:\d{2}:){2}\d{2}\s[A-Z]{3}\s\d{4}\n?){2,}
Regex101 Demo

Answer 2

SOLVED!
Got it using:
grep -v '^.*\(PDT\|PST\)\s*[0-9]\{4\}' -B 1 | grep -v '^--$'
Here is the final command:
cat certbot.log |
grep -v '^-*$' |
grep -v '^Processing ' |
grep -v '(skipped)' |
grep -v 'No renewals were' |
grep -v 'not due for renewal yet' |
grep -v 'No hooks' |
grep -v 'DeprecationWarning' |
grep -v 'not yet due for' |
grep -v '^Saving debug' |
grep -v 'Installing Python packages' |
grep -v 'Creating virtual' |
grep -v '^.*\(PDT\|PST\)\s[0-9]\{4\}' -B 1 |
grep -v '^--$' |
sed '/\(PDT\|PST\)/i\\n' |
sed 's/.*\(PDT\|PST\).*/--- & --- /'
Here is the final result:
--- Fri Mar 3 01:11:01 PST 2017 ---
Upgrading certbot-auto 0.11.1 to 0.12.0...
Replacing certbot-auto...
Installation succeeded.
--- Thu Mar 23 01:11:01 PDT 2017 ---
WARNING: unable to check for updates.
--- Wed Mar 29 01:11:01 PDT 2017 ---
Cert is due for renewal, auto-renewing...
Renewing an existing certificate
Performing the following challenges:
http-01 challenge for {mydomain}.com
Waiting for verification...
Cleaning up challenges
Generating key (2048 bits): /etc/letsencrypt/keys/0001_key-certbot.pem
Creating CSR: /etc/letsencrypt/csr/0001_csr-certbot.pem
new certificate deployed without reload, fullchain is
/etc/letsencrypt/live/{mydomain}.com/fullchain.pem
Congratulations, all renewals succeeded. The following certs have been renewed:
/etc/letsencrypt/live/{mydomain}.com/fullchain.pem (success)
--- Thu Apr 6 01:11:01 PDT 2017 ---
WARNING: unable to check for updates.
--- Fri Apr 7 01:11:01 PDT 2017 ---
Upgrading certbot-auto 0.12.0 to 0.13.0...
Replacing certbot-auto...
Installation succeeded.
--- Fri Apr 21 01:11:01 PDT 2017 ---
WARNING: unable to check for updates.

Answer 3

If you perl installed, try running this on the shell:
perl -0777 -ne 'while(m/^(.*?succeeded\..*?\d{4}.)|WARNING:.*?\./simg){print "$&";}' your_file
Output:
Fri Apr 7 01:11:01 PDT 2017
Upgrading certbot-auto 0.12.0 to 0.13.0...
Replacing certbot-auto...
Installation succeeded.
WARNING: unable to check for updates.
Regex Demo