Using the present tense for future events indicates certainty, consistency, and familiarity. In other words, use this to talk about events which will happen, which happen on a regular basis (or are predictable in some way), and about which you have some personal knowledge.
The holidays start next week.
I know this happens every year, last year I saw it happen in the same way, and I am sure it will happen the same way this year.
The train leaves in five minutes
I know the train leaves at a specific time, I know that trains usually leave on time, and I have seen the schedule to confirm when the train will leave.
The gala event starts tomorrow
I have personal knowledge that it is scheduled for tomorrow, I know that events like this usually start on schedule, and I feel comfortable asserting that it will definitely happen.
If any of these three does not exist, there is uncertainty, and the future tense will be more appropriate.
We get paid on Friday
I know this happens with some consistency and regularity, as I've already received at least one paycheck on Friday.
We will get paid on Friday
Oops, now there is some doubt. I hope this will happen, but I'm not sure it'll happen.
Here's another example: given no other context, consider these two sentences:
He will make the winning shot of the game in twenty seconds.
He makes the winning shot of the game in twenty seconds.
The first indicates a future condition, but the context is unclear. Do I really know this will happen? Probably not. More likely I'm expressing an opinion, or a personal hope.
But the second sentence, that expresses an odd certainty. The context is either that we are watching a recording of the game which I have seen before, or that I'm psychic, and I've already seen this happen with my mental powers.
Future indicative:
The bus is leaving in ten minutes. grammatical
The bus is going to leave in ten minutes. grammatical
If things go as usual or if things are to go well:
The bus should leave in ten minutes it usually leaves then.
The bus should leave in ten minutes. or it will be late
Requirement:
The bus is to leave in ten minutes. This bus must leave in 10
minutes
The bus shall leave in ten minutes. ditto†
The contract states that "Supplier shall deliver the merchandise not
later than the 15th day of each month" and that "Customer may
terminate this agreement early without penalty should Supplier ever fail to make a
timely delivery."
†Some speakers use shall as well with future indicative. That is exceedingly rare in AmE.
Best Answer
In non-formal conversation this is fine, except it needs more articles:
It's barely acceptable in formal use, too; but as a matter of courtesy to your readers it is desirable to pin down your time references a little more precisely. Otherwise readers will see was taking and assume that it refers to that day, and then have to revise that interpretation when they come to the next week. Write this instead:
Effective communication is driven by the principal of minimal effort; but that means very different things in written and spoken English, because the two media present radically different constraints:
Written English is governed by The Adamantine Law: Whatever can be misunderstood will be.
When you write you have no opportunity to correct your readers' misunderstandings. Consequently you must take care to express your thoughts as clearly and unambiguously as possible, so no misunderstandings arise. It is your reader's effort which must be minimized, not your own.
Spoken English, in contrast, is governed by The Tolerance Maxim: Whatever should be understood may be omitted.
When you speak you are engaged in a conversation. You and your interlocutors share extensive knowledge of the situation which need not be specified, you may speak elliptically and allusively in confidence that your interlocutors will fill in the holes and tacitly ignore or adjust any syntactical or grammatical blunders you commit. If significant misunderstandings arise, they may be corrected. All parties share the effort.