A past tense does not always have a past meaning. In some kinds of sentence we use verbs like I had, you went or I was wondering to talk about the present or future.

After if.

• If I had the money now I'd buy a car.
• If you caught the ten o'clock train tomorrow you could be in Edinburgh by supper-time.

Present Simple is used in complex sentences in subordinate clause after WHILE, BEFORE, AFTER, AS SOON AS, TILL, UNTIL.

• I’ll stay there until they come.
• He’ll have a party after he passes all his exams.
• Millie will definitely read all those books while she is on holiday.
• Before I leave you we’ll drink one for the road.
• I’ll get hold of this mansion as soon as she dies.