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Consider this phrase:

> 今は(event)二十分前です。

Deconstruction of the above phrase yields:

> Now is twenty minutes before (event).

**(Q1)** Can I reconstruct the statement using 後 in this manner?:

> 今は後で(event)に二十分がある。(I'm not sure if I used に correctly here)
>
> (There are twenty minutes from now to (event)).

**(Q2)** Can `今は` and (event) be elided once the context is set? That is to
say `二十分前です` and `後二十分がある` are acceptable phrases?

I think that (event) cannot be elided to form `二十分前です` and yet retain the
meaning. By itself the phrase would mean "(it was) twenty minutes ago" and
would be too vague to be useful to specify (event) in relation to "now".
CC BY-SA 3.0
2011-08-15T15:57:32.977
2662
2011-08-15T16:17:34.463
2020-06-17T08:18:27.500
-1
542
question
word-choice phrase-requests ellipsis
前 or 後 when placing an event in temporal reference to "now"
Notice that `は`is a topic marker, and there is often a corresponding form
without the use of such particle. In this case, the correct standard form will
be using `から`

> 今 **から** その式まで時間が後二十分ある。

  1. When you topicalize a modifier (as opposed to an argument), the postposition cannot be omitted, so it has to be `今からは`, not `今は` (except when you use `今` adverbially).
  2. The subject `時間が` is omittable. But note that `二十分` is adverbial, and does not take `が`.

So the form closer to your example is

> 今からはその式まで後二十分ある。

You can elide `今からは`

> 二十分前です。  
>  その式まで後二十分ある。
CC BY-SA 3.0
2011-08-15T16:17:34.463
2663
2011-08-15T16:17:34.463
2662
answer