“Wasn't” vs “weren't”
On a Tuesday morning, which of these sentences is the better way to express that I already want it to be Friday?
I wish it were Friday.
I wish it was Friday.
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The keyword you're looking for is not “future tense”, but “subjunctive mood”. The subjunctive mood in your case is “I wish it were Friday”, which conveys this meaning fully. It is to be noted, though, that the usage of this mood is decreasing, and it can be considered correct in all but formal environments to say “I wish it was Friday”.
"I wish it were Friday" uses the past tense of the subjunctive mood, which is the tense used to express wishes (but it is also used for imaginary or hypothetical situations).
The NOAD reports this notes about the subjunctive mood: