Use the future tense to indicate action that will occur at some point after the present. You can express future tense by using a verb in the simple present with a future adverb, by using the auxiliary will, or by using the expression is going to or are going to.
The spring term begins in January next year.[future tense expressed with simple present verb]
Each second, in the superheated core of the sun, 4 million tons of matter
are turned into pure energy. This process is the byproduct of a nuclear reaction
that converts nearly a billion tons of the simplest element, hydrogen, into a
like amount of the slightly more complex element, helium. This conversion of
hydrogen to helium, however, is a one-way street and eventually the Sun
will simply run out of fuel. At that
point, the energy to sustain the thermal pressure of the core will
disappear and the Sun will begin to shrink.
[future tense expressed with will]
--David Helfand, "Supernovae: Creative Cataclysms in the Galaxy"
The software company will come out with a new operating
system next year. [future tense expressed with will]
The software company announced that it is going to come
out with a new operating system early next year. [future tense
expressed with is going to or are going to]
You can describe a past action that was in the future of another past action by using the past tense of the auxiliary will.
The company promised it would deliver the prototype on time.