Instant
It means "a moment", or a very short time.
A moment is not a fixed amount of seconds; a moment simply means "a short time". Depending on the context, that may mean less than a seconds, a few days, or a million years.
It means a tiny period of time, such as--> I will be there in a moment.
Lasting for a short time, or a brief moment.
An indefinitely short period of time, a very brief portion of time as in an instant
Done in a moment; continuing only a moment; lasting a very short time; as, a momentary pang.
"un court moment, un instant"
You may be thinking of Judaism, but the description you use is quite a ragged one. The Jewish sabbath begins a short time before sundown on Friday, and ends a short time after twilight on Saturday. But that is by no means the only time when Jews worship.
With BST (British Summer Time) at the moment. BST ends on the 31st October 2010.
"Short on time" is the correct phrase. It means lacking sufficient time for a particular task or activity.
It covers a short period of time. apex
No, it is not. It is a noun usually meaning a short period of time (with the adjective form momentary).