"The identity of 'imap.gmail.com" cannot be verified."

When I try to access Gmail, Google, and a variety of other websites that I assume incorporate Google in their services, I receive some variation of this message: "the identity of 'imap.gmail.com' cannot be verified." This is also affecting my Mail app and its ability to receive mail from my Gmail account. This problem is affecting both Chrome (Version 38.0.2125.101) and Safari (Version 8.0.5 (10600.5.17)) on my MacBook Pro (2.5 GHz Intel Core i5, 4 GB 1600 MHz DDDR3, 360.08 GB free of 498.88 GB). I have cleared the cache on Safari and I have also made sure that the time and date on my computer are correct (two suggestions that I have pulled from other forums) yet the problem persists. I am not encountering this problem on my iPhone 4.