When a 13th century timewarp swallows a disillusioned mathamatician in the middle of his calculus exam, he is stranded by time, with 20 minutes left to finish the test he must calculate the years and circumnavigate fate in his final answer.

Something else to maybe consider, particularly in regards to time travel stories and ticking clocks -- in Back to the Future Marty is trapped in 1955, and his only hope back to the future (present) is the lightning strike on the clock-tower -- one tiny little shot and a clear and present ticking clock (and it's literal as it takes the form of a CLOCK tower...)-- he HAS to get his parents together before that lightning strikes or he'll either cease to exist, or at best, be trapped in good ol 1955 for good. Mega high stakes and a loud clicking clock.

In Bill and Ted's Excellent Adventure -- they too are trapped in a time warp as the antenna on their public phone cum time machine is busted -- what's the ticking clock? They have to present their history project by the close of the school day. As Nicholasanrewhalls mentioned, they do a bit of tom foolery to work around this when they end up getting locked up -- but still they are trapped, and there is a deadline.

In Hot-tub Time Machine -- they have to retrieve the can of Chernobly before a certain time (12 o'clock -- or something, I forget...) or they too will be trapped in 1986...

So -- If your Math guy gets caught in a time warp, trapping him in the 13th century, what does he have to do to get back?

Anyway -- good luck with it. Hopefully my earlier post doesn't come across too harshly -- I've just got a thing about time travel movies :)

As stated above; your time clock doesn't work if the character has the ability to travel through time (Bill and Ted got away with it because their concept of time travel was goofy as hell. Back To The Future used the ability to come back at an earlier point in time as a plot point).

Aside from the above telling us that a mathematician is transported back to the 13th century, we have no idea what, once there, the objective goal is, how it is linked to travelling back in time, who is trying to stop your protagonist from achieving that goal, or what the stakes of failure may be.

Worth repeating:

A logline should tell the reader exactly what they can expect to see in your movie on ONE read, not two?three?four? five? etc etc etc?