They are looking forward to their wedding. They are going to be getting married to each other in just a few days.
At the start of the play, these two are looking forward to their marriage. In fact, they cannot wait. They are talking about how impatient they are for the day to come. They are eager even though Theseus apparently first won Hippolyta with his sword.
By contrast, Hermia is not at all eager to marry Demetrius, and that will be the reason for the rest of the play to happen.
The main events in the play surround the concept of love. Theseus and Hyppolita are looking forward to their marriage in fourteen days. This factors heavily into the theme of love and of relationships as they are paralleled by the young lovers, the star-crossed relationships of the youth, as well as the relationship between Oberon and Titania in the woods. In fact, it is the idea of marriage that sets the plot in motion for Egeus wants his daughter Hermia to get married to Demetrius, but Hermia is in love with Lysander. Helena, Hermia's friend, is in love with Demetrius, who is not in love with her. It is Hermia's plan to run away with Lysander that takes the action to the woods in the first place where Theseus and Hyppolita reappear in the stormy relationship of Oberon and Titania. After a great deal of meddling and the misadventures of a sprite named Puck who drives the action, ultimately, the play ends in a group wedding and alls well that ends well.
The opening lines of the play clearly specify that both Theseus the Duke of Athens and Hippolyta are eagerly and impatiently waiting for their marriage to be solemnized in the next four days:
Now, fair Hippolyta, our nuptial hourHIPPOLYTA Four days will quickly steep themselves in night;
Draws on apace; four happy days bring in
Another moon: but, O, methinks, how slow
This old moon wanes! she lingers my desires,
Like to a step-dame or a dowager
Long withering out a young man revenue.
Four nights will quickly dream away the time;
And then the moon, like to a silver bow
New-bent in heaven, shall behold the night
Of our solemnities.