FASTING sollte das natürlich heißen :-)

In conversation, someone might explain it like this:
The night before the test, ...
... you can't eat (or drink?) anything after 10 p.m.
... you have to fast from 10 p.m. onward.

In writing, the instructions might be shorter:
Nothing by mouth after 10 p.m. the night before.
Nothing but water from 10 p.m. onward.

Remember that we use the 12-hour clock in English. (-:

'As of' is for data that has been reported but that will change again: preliminary election results as of the hour the polls closed; first-quarter financial report as of March 31; etc.

hm-us: many thanks... as to the 12-hour clock: in conversation you would probably not say "I'll be there at 18 h tonight" but O noticed that in offical/formal texts sometimes a 24-hour time is used (and as far as i remember that was in Seattle, WA), such as "the meeting is scheduled for 15 h."
Or maybe I am wrong...?

In my experience, in the US that would only be likely in the military. Or maybe in an organization with many ex-military employees -- a large one near Seattle comes to mind. (-; Even in military jargon, I would have expected 1500h (pronounced 'fifteen hundred hours'), not 15 h, but that's only my impression as a layperson.

That said, it's certainly possible that any large international corporation (another one in that area comes to mind) might decide to use the 24-hour clock for internal communications, just because it's the majority preference in other countries and/or because it seems more scientific.

But for anything aimed at the general public, I wouldn't recommend it. Most ordinary Americans would have to stop and count on their fingers. Even train and airline schedules where space is an issue tend to be written in a format like 1115a, 0135p, etc., to prevent confusion.

>In writing, the instructions might be shorter:
you will also see "Nil by mouth", at least in the UK


"Early enteral feeding versus "nil by mouth" after gastrointestinal surgery: systematic review and meta-analysis of controlled trials"
http://www.bmj.com/cgi/content/full/323/7316/773

I agree with the others that in the US, the 24-hour clock is rarely used in normal contexts. It's routinely used in the military, and occasionally in other contexts (for example, among computer programmers), but elsewhere not at all. Most people would not understand if they read that a performance begins at 19.30 (or 19:30 or 1930). (People who had visited Europe might understand, but even so, they would wonder why it was expressed in this non-standard way.)

As to the original question you could say:
from 10 pm on ("onwards" sounds over-formal to me)
after 10 pm
later than 10 pm

and in any of these contexts you can replace 10 pm by:
10 PM
10:00 (if it's clear that evening is meant)
10:00 PM
10 o'clock
10 in the evening
10 at night