You use until with a negative to emphasize the moment in time after which the rest of your statement becomes true, or the condition which would make it true. The traffic laws don't take effect until the end of the year It was not until 1911 that the first of the vitamins was identified. = till Until is also a conjunction. The EU will not lift its sanctions until that country makes political changes. = till
If something happens until a particular time, it happens during the period before that time and stops at that time. Until 1971, he was a high-ranking official in the Central Communist Committee. consumers who have waited until after the Christmas holiday to do that holiday shopping. = till Until is also a conjunction. I waited until it got dark Stir with a metal spoon until the sugar has dissolved. = till
To; up to; till; before; used of time; as, he staid until evening; he will not come back until the end of the month