1. a. The preposition By is used to refer to a deadline or a due date.
For example:
- The manager needs the final report by the twenty-sixth of September at midday.
- The birthday cake needs to be in the oven by eleven a.m. or else it won’t be ready on time.
- “If I don’t find a new chef by Monday, I will have to close the restaurant” the owner told his worried staff.
1. b. We can also use By to say should happen no later than a certain time.
For example:
- The new employee should arrive no later than 9 a.m. OR The new employee should arrive by 9 a.m.
- The bus should leave the terminal no later than midday. OR The bus should leave the terminal by midday.
2. The prepostion Until, on the other hand, refers to the time before a deadline or up to a certain period of time.
For example:
- The legal team has until Thursday to prepare its opening statement in court. Today is Monday that means they only have two full days to prepare.
- The student was studying until midnight last night, he was preparing for his final university exam.
- To make tea, you have to wait until the water is boiled, once the water is boiled you can pour it into the teapot.
- The teenager waited until her parents were in bed before she snuck out of the house and met up with her friends in the park.
3. Up To has a similar meaning to Until, however we tend to use up to when referring to an action that took place up to a certain point in time.
For example:
- Up to yesterday, the family had no idea about the money hidden in the walls of their home.
- The students had up to today to decide what topic they want to research for the final project of the year. Now they have to tell their teacher which topic they chose.
- It took the politicians up to five months to agree on how to handle the economic crisis in their country.
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