Exception Thrown error while attempting to log in

I’m using deluxe hosting, with 2 different WordPress installations (both WordPress 4.9.5). The two sites are virtually identical in terms of plugins & content (one is the development site; the other is the live site).

While trying to log in to the live site earlier today, I received the following error message:

Exception thrown
DateTime::__construct(): Failed to parse time string (@) at position 0 (@): Unexpected character

Logging into the development site yielded no such error.

This error persisted on the live site for 15-30 minutes, after which I was able to successfully log in.

Does this sound like a hosting issue, a WordPress issue or a plugin issue?