One of the most important features in Civilization IV was the clock. It allowed you to both see how long you've been playing and also set an alarm. From the manual:
CLOCK SCREEN
The Clock Options Screen lets you turn on and off a clock to time how long you’ve been playing, as well as set an alarm to let you know when you should stop playing and go to work. Or eat.
After playing Civilization V until past 4 AM (one more turn, I swear!), I've realized that I desperately need this feature.
Is there a way to turn on a clock, preferably one with an alarm but just a display of the time, in this game? I couldn't find it in the settings.
Sure, I could use my phone, but I'd like something more visible while I play. And since I charge it only when I sleep (rather than playing Civ), there's a fair chance that it's going to be dead long before 4 AM!
Best Answer
This feature isn't part of the base game, sadly. There are many mods that add a clock, for instance this Simple Alarm Clock mod.
Achievements and mods don't mix, though, so if you want achievements you might look into a DLC method, like Enhanced User Interface.
Really, though, the best solution for keeping track of time while gaming is something that isn't game specific. Yeah, today it's Civ5 keeping you up, but Civ6 is coming out in a few months...
My solution for this problem is Rainmeter on a second monitor. It can display performance stats as well, and it stays out of my way.
It's also possible to get a clock overlay using certain third party tools, this SuperUser question is a good set of solutions to that problem.
Finally, you can take the "low tech" route, and just use a small clock or stopwatch attached to your monitor's bezel, or some other convenient attachment point. I've used a watch face (minus the band) for this in the past.
I've also got a cradle made out of LEGO on my monitor stand where I put my phone to charge while it's on my desk - there are myriad solutions for alarm clocks on phone OS'es. Yeah, you charge while you're sleeping, but the cost of a spare charger versus the cost of not being a zombie the next day at work/school/whatever? Probably worth it :P