The following error may occur during the JunOS software upgrade process :
[Jul 28 15:11:32]: Checking pending install on fpc0
fpc0: Verify the signature of the new package verify-sig: cannot validate certs.pem certificate is not yet valid: /C=US/ST=CA/L=Sunnyvale/O=Juniper Networks/OU=Juniper CA/CN=PackageProductionSHA1RSACA/emailAddress=ca@juniper.net ERROR: Package signature validation failed. Aborting install.This is usually a sign that your Juniper device clock is way off. Check your clock using the following command :
show system uptime
To adjust your clock, do as followed :
set date YYYYMMDDhhmm.ss
Try upgrading again, the error should no longer be present.