https://letsencrypt.org/stats/
Let's Encrypt uses SHA256, so it wouldn't work on old OS, such as Windows XP less then SP3. Windows XP SP3 is OK.
https://support.globalsign.com/customer/portal/articles/1499561-sha-256-compatibility---------- Добавлено 02.02.2017 в 15:36 ----------
If you are not using certificate pinning, then yes.
At least, you can add additional cipher suites to support old browsers (even under Windows XP). To do so, add/change the following parameters in your apache configuration:
SSLCipherSuite EECDH+ECDSA+AESGCM:EECDH+aRSA+AESGCM:EECDH+ECDSA+SHA256:EECDH+aRSA+SHA256:EECDH:DES-CBC3-SHA:!aNULL:!eNULL:!LOW:!EXPORT:!DES:!RC4:!MD5:!EXP:!PSK:!SRP:!DSS:PSK-AES128-CBC-SHA SSLHonorCipherOrder on
Then test your website with the service mentioned above. If there will complaints about DH parameters, please let me know.
lustoff, I've checked your report and it is OK. However, you can tune the web server to support more browsers. Do you use a shared hosting or can change some web server parameters?
Please, show full report
https://www.ssllabs.com/ssltest/
there was no requirements for it. learn to lose with dignity :)
strtotime('first day of')-345600
miltorg, it is an integer number
fix your PHP and play with
echo date('r',strtotime('first day of today', strtotime('2017-03-05'))-432000);
